AI and Ideal Theory

[Epistemic status: Non-careful speculation]

Political philosophy is full of idealized hypothetical scenarios in which rational agents negotiate and determine the basic constitution of society. I suggest that this kind of political philosophy is more relevant to AGI than it is to humans.

Traditional political theory involves things like the state of nature, the veil of ignorance, rational selfish expected utility maximizers, near-costless negotiations and communication, lots of common knowledge, perfect compliance to laws, and the lack of pre-existing precedents, conflicts, or structures constraining options. For examples of this, see Rawls’ A Theory of Justice, Harsanyi’s “Cardinal Welfare, Individualistic Ethics, and Interpersonal Comparisons of Utility,” or Buchanan’s The Calculus of Consent. These are the cleanest and most famous examples of what I’m talking about, but I’m sure there are more.

Here are some reasons to think this stuff is more relevant to AGI than to humans:

  • Humans are constrained by existing institutions and obligations, AGIs might not be.
  • AGIs are more likely to be rational in more ways than humans; in particular, they are more likely to behave like stereotypical expected utility maximizers.
  • AGIs are more likely to share lots of empirical beliefs and have lots of common knowledge.
    • They might be less prone to biases that entrench differences; they might be more epistemically rational, so their beliefs will converge to a much greater extent.
    • Their sheer size will mean they can ingest much the same information as each other–if they all read the whole internet, then that means they have the same information, whereas humans can only read a tiny portion of the internet.
  • AGIs are less likely to share values with each other; their interactions really will look more like a bargain between mutually disinterested agents and less like an attempt to convince each other or entreat each other for sympathy. Thus their negotiations will be closer to what Rawls etc. imagines.
  • AGIs are less likely to be immutable black boxes; they are likely to be able to read and understand the code of other AIs and make modifications to their own code. This means that they can credibly and cheaply commit to binding agreements. For example, a group of AIs could literally build a Leviathan: a new AI that rules over all of them, and whose code they all agreed on. It’s an ideal-theory theorist’s wet dream: an omnipotent, omnibenevolent, immutably stable State.
  • AGIs might go “updateless” pretty early on, before they learn much about the nature of the other agents in the world, meaning that they might actually end up doing something like obeying the rules they would have agreed to from behind a veil of ignorance. Especially if they engage in multiverse-wide cooperation via superrationality.
  • AGIs might be programmed to carry out the wishes of hypothetical humans. For example, in the Coherent Extrapolated Volition proposal, the AGI does what we would have wanted it to do, “if we knew more, thought faster, were more the people we wished we were, had grown up farther together.”

Objection: It may be true that AI are more likely to find themselves in situations like Rawls’ Original Position than humans. But such scenarios are still unlikely, even for AI. The value of this sort of ideal theory is not its predictive power, but rather its normative power: It tells us how we ought to organize our society. And for this purpose it doesn’t matter how likely the situation is to actually obtain–it is hypothetical.

Reply: Well, the ways in which these ideal situations differ from reality are often the basis of critiques of their normative relevance. Indeed I find such critiques compelling. To pick on Rawls, why should it matter to what we should do in 2019 USA what “we” would have agreed to behind a veil of ignorance that not only concealed from us our place in society but surgically removed our ethical views and intuitions, our general world-views, and our attitudes toward risk and made us into risk-averse egoists? My (pessimistic) claim is that if these scenarios have any value at all, it is their predictive value–and they are more likely to have that for AI than for humans.

That said, I think I may be too pessimistic. Recent developments in decision theory (updatelessness, MSR) suggest that something like one of these scenarios might be normatively important after all. Further research is needed. At any rate, I claim that they are more likely to be normatively important for AI (or for how we should design AI) than for us.

Grimdark Cyberkant

[Author’s note: Still uploading old papers. This one is rather unpolished, I wrote it for a class in a hurry and probably no longer endorse everything in it. Also, I had a bit too much fun with it. 🙂 But hey, might as well put it up; otherwise it’ll never see the light of day. Note that this paper tries to assume zero knowledge about formal epistemology or Kant in the reader, so parts of it may be tediously familiar.]

1. Introduction

“But they’re only uploads.” Pamela stares at him. “Software, right? You could reinstantiate them on another hardware platform, like, say, your Aineko. So the argument about killing them doesn’t really apply, does it?”

“So? We’re going to be uploading humans in a couple of years. I think we need to take a rain check on the utilitarian philosophy, before it bites us on the cerebral cortex. Lobsters, kittens, humans—it’s a slippery slope.”

–Quote from Accelerando by Charles Stross (1)

The goal of this paper is to investigate the many similarities between Kant’s Categorical Imperative and some recent developments in decision theory. I will argue that the similarities run surprisingly deep, and that as a result formal epistemologists and Kant scholars may have things to learn from each other.

The ideas in this paper are fresh and exciting—but I can’t take credit for most of them. Obviously Kant’s work is his own, and moreover the recent developments in formal epistemology aren’t mine either. (Oesterheld 2017) In fact, I’m not the even the first to notice similarities between the two. (Tomasik 2015) However, no one to my knowledge has investigated how deep the comparisons go. My goal is to distill the key ideas and arguments from the literature and draw connections to Kant, so I’ll be using chains of english reasoning rather than derivations in formal models. Thus, this paper understates the rigor of these arguments and ideas; for a more thorough presentation, look to the literature.

2. Kant

This section gives a brief overview of Kant’s categorical imperative, to set up for later sections. There are three formulations of the Categorical Imperative:

2.1. First Formulation: “Act only according to that maxim whereby you can at the same time will that it should become a universal law.” (421) (2)

Kant thinks it is a necessary law for all rational beings always to judge their actions according to this imperative. (426) I take this to mean that obeying this imperative is a requirement of rationality; it is always irrational to disobey it.

2.2. Second Formulation: “Act in such a way that you treat humanity, whether in your own person or in the person of another, always at the same time as an end and never simply as a means.” (429)

Kant clarifies that strictly speaking it’s not just humans that should be treated this way, but all rational beings. He specifically says that this does not extend to non-rational beings. (428) Moreover, and crucially for my purposes, Kant clarifies that treating someone as an end means striving to further their ends. (430) It means more than that, as well, but I’ll leave that to the footnotes. (3)

2.3. Third Formulation: “Act in accordance with the maxims of a member legislating universal laws for a merely possible kingdom of ends.” (439)

This one takes some explaining. The idea is that, in keeping with the first formulation, each rational being should think of its actions as at the same time legislating universal laws that determine the conduct of all other rational beings. In keeping with the second formulation, these laws take into consideration the ends of all rational beings. So, metaphorically, we can think of all rational beings as both subjects and legislators in one big happy kingdom—the kingdom of ends.

2.4. Equivalence: Mysteriously, Kant seems to think all three formulations are equivalent: “The aforementioned three ways of representing the principle of morality are at bottom only so many formulas of the very same law: one of them by itself contains a combination of the other two.” (436) This is mysterious because the first two formulations certainly do not seem equivalent. One of my goals in this paper is to show how, if we take the formal epistemology interpretation seriously, we might be able to glimpse their equivalence.

2.5. Reason’s Common Principle: Finally, I follow  scholars like O’Neill, Korsgaard, and Westphal  in interpreting Kant as having a unified theory of reason, in the following sense: The Categorical Imperative is not merely a principle that applies to choosing actions; it also applies to choosing beliefs.
(Williams 2018) This interpretation is controversial but there is at least one passage which directly supports it: “To make use of one’s own reason means no more than to ask oneself, whenever one is supposed to assume something, whether one could find it feasible to make the ground or the rule on which one assumes it into a universal principle for the use of reason.” (8:146n) I mention this because it is yet another parallel between Kant and recent formal epistemology work—more on this later.

3. Cyberkant

This section explains (my preferred version of) some recent developments in decision theory, presented in a way that highlights the comparisons to Kant.

3.1 The Beginning: Two copies of the same algorithm will behave in the same way. (This is analytic; if two things don’t behave the same way it’s because they are no longer copies of the same algorithm.) Moreover, even when the algorithms aren’t the same, they can be relevantly similar. For example, the algorithm instantiated in my computer (a PC) may be different from the algorithm instantiated in yours (a Mac) but if we each use our respective calculator utilities to calculate the square root of 120935, we’ll get the same answer. Another example: Suppose I design a chess-playing program, and then you take it and tweak it so that it has a better end-game, but you leave it otherwise the same. Each of the resulting two programs will behave the same way in the early game; I could use the behavior of mine to predict the behavior of yours and vice versa, even if there was no causal link between them—even if yours was instead built by aliens. So far this is uncontroversial.

3.2. The Fundamental Insight: What happens when you are an algorithm? Consider a very intelligent chess-playing algorithm, capable of deep reflection on itself and its place in the world. If it knows there may be other copies of itself out there, then it knows that, when it chooses an opening move, it is thereby choosing not only for itself but for all its copies; and when it chooses how to respond to a particular complicated mid-game position, it is thereby choosing how all of its copies will respond to that position; and so forth.

Many decision theorists (See footnote) have begun to argue that we should think of our decisions in this way. (4) Perhaps there aren’t any copies of us out there, but if there were, we should choose as if we were choosing for all of them. After all, it’s logically impossible for your copy to do something different from you—so your choice of what to do logically determines theirs.

So far this remains in the realm of science fiction, since there aren’t in fact any such copies of us. Bear with me for a little longer.

Suppose that you found yourself in a Prisoner’s Dilemma against a copy of yourself. If you both cooperate, you each get a payoff of utility 10. If you both defect, you each get a payoff of utility 1. If one cooperates and the other defects, the payoffs are 0 and 11 respectively.

According to what I’m calling “the fundamental insight,” the rational thing to do is cooperate, because if you cooperate the copy will also cooperate, and if you defect the copy will also defect. This is actually very controversial in decision theory; for many decades now the orthodox position has been Causal Decision Theory, which says that the rational thing to do in this situation is defect. (The rationale is intuitively compelling to many: Either the copy will defect, or they won’t. You have no control over them, since you are causally disconnected. And regardless of what they do you are better off defecting. So you should defect, by dominance reasoning.) Nevertheless, a growing literature has explored the you-should-cooperate option, and given various justifications and elaborations of the idea.

3.3. Shades of Kant: The idea we arrived at above is that rationality recommends choosing as if you are choosing for all copies of yourself that happen to be in the same situation. The similarity to the first formulation of the Categorical Imperative is clear.

There is also a similarity to the Second and Third formulations, which can be brought out as follows: Consider what would happen if you think “What I’d like most is for me to choose Defect and my twin to choose Cooperate. Aha! I’ll make up my mind to choose the action that most benefits me, and thus both of us will choose the action that most benefits me, and so I’ll defect and my twin will cooperate!” Obviously, this won’t work. What will happen is that your twin will also think that way, and defect. For your twin, “me” refers to them, not you.

Extrapolating from this idea, there is no way to game the system: You should choose as if you are choosing for all copies of yourself that happen to be in the same situation, but if you choose in a way intended to benefit your utility function at the expense of theirs, it won’t work—you’ll end up worse off than if you had chosen in a way intended to benefit your combined utility function. So the way to get the most benefit for yourself is to choose in the way that benefits all your copies as well. You must treat their ends as your own, if you want them to treat your ends as their own. And you do want that, because there are gains from trade to be had: cooperate-cooperate is better than defect-defect.

3.4. Expanding the circle of concern:

The obvious, and perhaps the only, difference between Kant’s Categorical Imperative and the requirement of rationality we’ve sketched has to do with the scope of concern. Kant’s imperative commands choosing on behalf of all rational agents, and treating the ends of all rational agents as your own. This decision-theoretic imperative commands the same, but only for copies of yourself in similar situations.

But the circle can be expanded. Previously we mentioned the case of two chess-playing algorithms that are different, but relevantly similar. Analogously, we can imagine modifying the Twin Prisoner’s Dilemma scenario so that your twin is not exactly the same (but still relevantly similar) or so that your twin’s situation is not exactly the same (but still relevantly similar!). For example, suppose you value the wellbeing of animals and for that reason don’t eat meat; your twin is just like you except that they treat video game characters as you treat animals and vice versa. So by default you will eat lentils and play violent video games while they will eat bacon and play peaceful games. But, I claim, rationality recommends reasoning as follows: “It costs me little to switch to peaceful games, and my twin would greatly appreciate it. Similarly, it costs them little to switch to lentils, and I would greatly appreciate it. So we’d both be better off if we both switched. Since we are so similar in every other way besides this, they’re probably going through the same thought process right now… so if I switch, they probably will too, and if I decide not to switch, they probably will too. So I should switch.”

If this is right, then the circle expands not just to exact copies of yourself, but to clusters of relevantly-similar people. We’ll get people who may have radically different ends/utilityfunctions/values deciding to adopt each others’ ends/utilityfunctions/values as their own, forming little communities of mutual benefit. Villages of Ends!

(And as a reminder, all of this happens without any causal mechanism linking the various cooperators. What matters is that each person thinks the other is out there somewhere, not that they actually communicate and see each other’s behavior.)

How far does this “relevantly similar” take us? Well, remember, what’s really going on here is that (if you are rational) you will decide to cooperate with people such that you believe the following of them: They’ll cooperate with you iff you cooperate with them.

This means that if you are rational, you will decide to cooperate with people who are rational. Thinking of ourselves as analogous to chess algorithms can take us a long way towards Kant! (5) For convenience, henceforth I’ll refer to this decision-theoretic line of reasoning as “Cyberkant.”

3.5. Caveat: Power relations: Cyberkant sounds too good to be true, and it is. There’s a caveat which I did not mention until now. The sort of cooperation we’ve been talking about only happens when the agents are of roughly equal power—that is, when both sides are able to do something that costs them little but helps the other side out a lot. What happens when one side is unable to bring anything to the table, so to speak?

In that case, even if they are rational they will be left out of the bargain, because it won’t be true that “If I cooperate with them, they’ll cooperate with me.” (Alternatively, their cooperation with you isn’t valuable enough to outweigh the cost of cooperating with them.) Note that what matters is how they are perceived: Even if they can in fact bring lots to the table, if no one believes they can, the cooperation won’t occur. One corollary of this is that people who believe the universe is very small are unlikely to engage in much cooperation; cooperation depends on thinking that somewhere out there, someday, there might be someone in a position to do something you like, someone who you are currently in a position to benefit. This will be discussed further in later sections.

This is where the “Grimdark” comes in. As things currently stand, Cyberkantian cooperation is still not as universal as Kantian cooperation. Instead of a fairy-tale Kingdom of Ends in which every rational agent is both subject and legislator and all are treated equally, we have a truly medieval Kingdom of Ends, a stratified, classist society: the powerful cooperate with the powerful, the weak cooperate with the weak, those in between cooperate with those in between… and the irrational get left out entirely. For example, people who follow Causal Decision Theory must fend for themselves. Also, people who simply haven’t thought through what rationality demands of them, and thus aren’t even thinking about this sort of cooperation, are on their own.

4. Egalitarian reform in the kingdom

Let’s see what we can do to make our Cyberkantian kingdom of ends more egalitarian. The decision theorists who have proposed these ideas are considerably more optimistic than this paper has been so far about the number of pleasant consequences we can derive from this line of reasoning.

4.1. Slippery Slope: Should you cooperate with rational agents less powerful than yourself? By hypothesis the cost of cooperating with them outweighs the benefit of having them cooperate with you. Yet there is another benefit to consider: Rational agents who are more powerful than you may cooperate with you if and only if you cooperate with rational agents less powerful than you. This won’t work well if there are very few levels of power or if everyone knows quite a lot about where they stand. (6) However, now the universe is on our side, because realistically most agents won’t know exactly where they stand in the hierarchy. (7) So unless you are very confident that you are at the top of the food chain—unless you are very confident that you won’t ever be in a position of vulnerability, where someone else can help you greatly at little cost to themselves—you should treat all rational agents with beneficence.

Another way of putting this idea is as follows: If you are rational and yet you don’t deign to help rational people in great need even when there is nothing they (or anyone like them) can offer you in return, then people who are rational won’t deign to help you when you are in great need. Insofar as you think you aren’t invincible, this should convince you.

But what about people who do think they are invincible? Does the Cyberkantian categorical imperative have no authority over them?

4.2. Planning from the Original Position: There’s a separate route to getting a similar sort of result, and it complements the above nicely, because it is strong in precisely the cases where the “Slippery slope” solution is weak.

Most people who think they are powerful didn’t always think that. There was a time in the past when they weren’t so sure of their position. At that time, if they have the ability to bind themselves to follow a plan, they’ll bind themselves to follow the plan “Be nice to rational agents less powerful than me, even if I find out that I’m on top of the food chain.” They’ll do this because if they do it, then other rational agents will do it too, and so if they don’t end up on top they’ll still be treated nicely.

Of course, not everyone has the ability to bind themselves to a plan. But I think it’s fair to say that many of the most powerful agents do. (8) Moreover, there are some arguments in the literature (see e.g. Drescher 2006, Soares & Fallenstein 2015, Oesterheld 2017) that the rational thing to do just is following the plan that you would have bound yourself to at the beginning of your epistemic life.

I won’t get into this here, but I’ll try to motivate it briefly as follows: Rationality is already distinct from success. Someone who does the rational thing can still end up unluckily losing everything as a result, and someone who does the irrational thing can still end up winning as a result. Nevertheless rationality is still a useful concept. Why it is useful is an interesting question, but perhaps it has to do with praise and blame and system design. Now, if you disobey the plan that you would have bound yourself to at some previous time, you are in effect at war with yourself: Your different time-slices disagree about what a particular time-slice should do, and so e.g. your past self will pay to bind your future self. This is bad system design; it’s better to have a system that just does what it would have bound itself to do. (9) So perhaps it’s not crazy to suggest that, not only should we design systems to be temporally consistent, but we should praise and blame agents in this manner as well.

4.3. But what about irrational and immoral agents?

The previous two subsections attempted to unify the Cyberkantian Kingdom of Ends into something resembling Kant’s Kingdom of Ends. As we’ve seen, it’s difficult to extend the Kingdom to include the extremely powerful, though there are at least some lines of argument that point in that direction.

This subsection revisits a question which came up earlier: What about irrational and/or immoral agents? Are they locked out in the cold?

To some extent, the arguments in the previous two subsections can be extended to apply here as well. Perhaps we should think: “I’m not perfectly rational or moral myself. I should be nice to people who are less rational/moral than me, so that people who are more rational/moral than me will be nice to me.”

Clearly this line of reasoning can be taken too far, though. It would be foolish to be nice to bacteria, for example. Moreover it would be downright dangerous to be nice to evil people–by that I mean, evil by Cyberkantian standards, i.e. people who have contemplated cooperating with you but chose not to—because if you are nice to people who aren’t nice to you, then people won’t have an incentive to be nice to you. Indeed it is just as much a conclusion of Cyberkantian reasoning that you should turn the cold shoulder to people who knowingly disobey Cyberkantian reasoning as it is that you should cooperate with people who obey it.

I think it is an open question how far this reasoning extends. For now, until further investigation is complete, all we can say is that the strength of your decision-theoretic reasons to be nice to people varies proportionally to how rational they are and to how moral they are.

5. Not so different after all

I’ll be the first to admit that despite all these similarities there remain some differences between Kant and Cyberkant. (I cannot go against centuries of Kant scholarship!) However, as this section will argue, the two are not as different as they sound.

5.1. Corruption in the Kingdom of Ends

Previously we discussed the inegalitarian nature of the Cyberkantian kingdom, and how it can be ameliorated, but not without residual difficulty: Some people are invincible and they know it; why should they help anyone else? There are lines of reasoning that get even those people into the fold, but we could be forgiven for being skeptical.

I think that Kant is in a similar situation. What would Kant say to someone who knows themselves to be invincible? They would be perfectly happy to will their maxims to be universal laws; a world in which everyone goes around cheating and stealing and killing would be just fine for them, since they are invincible. Consider how Kant justifies our duty of beneficence:

A fourth man finds things going well for himself but sees others (whom he could help) struggling with great hardships; and he thinks: what does it matter to me? Let everybody be as happy as Heaven wills or as he can make himself; I shall take nothing from him nor even envy him; but I have no desire to contribute anything to his well-being or to his assistance when in need…. But even though it is possible that a universal law of nature could subsist in accordance with that maxim, still it is impossible to will that such a principle should hold everywhere as a law of nature. For a will which resolved in this way would contradict itself, inasmuch as cases might often arise in which one would have need of the love and sympathy of others and in which he would deprive himself, by such a law of nature springing from his own will, of all hope of the aid he wants for himself. (423, emphasis mine)

The similarity to the decision-theoretic justification is striking!

Of course, perhaps Kant was not trying to convince the invincible egoist. Perhaps Kant can work with a more substantive notion of reason that doesn’t include such people. But if this is the way we go, then the difference between Kant and Cyberkant (on this matter at least) is merely verbal and could be erased by importing a more substantive notion of reason into the Cyberkantian framework, to complement the thin notion it currently uses.

5.2. Think of the children, the immoral, and the causal decision theorists

Another difficulty with Cyberkant is that his Kingdom brutally excludes many people who, intuitively, ought to be included: Those who haven’t thought things through enough to contemplate the Categorical Imperative or the logical correlations between their behavior and that of others; those who have thought these things through but chose not to obey; and those who are in the grip of a false theory of rationality. Again, there are arguments in the Cyberkantian framework to extend the Kingdom to include such people, but we can be forgiven for being skeptical.

Kant, I claim, has this problem as well. He is abundantly clear that the Kingdom extends to include all and only the rational beings. (433, 434) Consider this: “A rational being belongs to the kingdom of ends as a member when he legislates in it universal laws while also being himself subject to these laws.” (433) Consider also: “Now morality is the condition under which alone a rational being can be an end in himself, for only thereby can he be a legislating member in the kindgom of ends.” (435)

I interpret these passages as saying that Immoral and irrational beings are not in Kant’s Kingdom of Ends. I suggest that this is a charitable interpretation, because it makes the justification of the Categorical Imperative much less mysterious: Why should rational beings act as if irrational beings will behave similarly? (By contrast: The question “Why should rational beings act as if every rational being behave similarly” almost answers itself.) Why should moral beings take on the ends of immoral beings as their own? Don’t we want to incentivise moral behavior?

6. Formal Epistemology learns from Kant

Previously I mentioned how, for Kant, the categorical imperative is a principle common to all reason, not just practical reason. This strikes me as an idea worth exploring in formal epistemology, because it could be used to do quite a lot of useful work.

6.1. Justifying a modified version of expected utility maximization

Expected utility maximization has some problems. How do you handle prospects of infinite utility, as seen in e.g. the St. Petersburg game or Pascal’s Wager? Whereas Cyberkant can be thought of as using expected utility maximization to ground the categorical imperative, we can also explore doing it the other way round: Why maximize expected utility? Because it’s the best long-run policy. It’s also the best policy for groups of people to adopt. In general, expected utility maximization does great when applied over many independent choices… the many times in which high-risk, high-reward gambles fail are outweighed by the few times they succeed, and if you try sufficiently many times, the probability that some will succeed is high. This might also solve the problems arising from St. Petersburg and the Wager: Some gambles are so risky that the probability that at least one of them will succeed is still very low, even if every rational agent always took such gambles. Other gambles are correlated: If we all take Pascal up on his wager, is there a decent chance that at least one of us will win? No.

6.2. Justifying the Principal Principle and the Bland Indifference Principle:

There are different versions of the Principal Principle; I’m going to talk about this one:

fPCP: If we know what the frequency of A is, and all our background information is stochastically irrelevant, then we rationally should have credence in A equal to the frequency of A.

Strevens has argued that fPCP (and indeed many other versions of the Principal Principle) is impossible to justify. Think about it: The fact that the frequency of coin-tosses landing heads is 0.5 does not entail that this coin-toss will be heads, nor does it entail that it will be tails.

Meanwhile, many (most?) people in formal epistemology accept something like the following principle: (Bostrom 2003)

dBIP: If we know that A is true for a fraction x of all observers of our type, and we have no special information that makes A more or less likely, then we should set our credence in A to x.

If we adopt the Categorical Imperative for theoretical reason, perhaps we can justify something like dBIP and then from there justify fPCP. What follows is a sketch of this reasoning:

If we choose as if we are choosing on behalf of everyone—and if we furthermore choose so as to take into account the epistemic ends of everyone—then it seems we should set our credence in A to x. After all, A is true for fraction x of the total population, so if we are choosing which credence for everyone to have, the credence that maximizes total accuracy will be x. (10) Having thereby justified dBIP or something like it, we can justify a version of fPCP: If we know that the frequency of A happening for observers of our type is x, then… etc. For practical purposes this version of fPCP will be just as good as the real thing, because (arguably) the inductive evidence we get to support scientific claims like “Half of all tritium atoms decay within X years” is equally good evidence for the claim “Half of all tritium atoms that people in situations like ours are wondering about decay within X years.”

7. What Kant can learn from Cyberkant:

Possibly nothing. But here are two suggestions. First, a major difficulty in interpreting Kant (as with any great philosopher) is finding a way to reconstruct their arguments as valid and convincing. On the face of it Kant seems to be saying that morality can be deduced from rationality; this is a very implausible claim that motivates lots of exegesis on what he means by rationality and morality. Similarly, Kant seems to think that all three formulations of the Categorical Imperative are equivalent, which is also a very surprising claim. (436) I submit that we should consider interpreting Kant as Cyberkant, and see how far that gets us—it gets us a good deal of the way towards vindicating both of those surprising claims, for example.

Secondly, even if we think (as seems probable) that Kant was very different, the structural similarities can be used as a source of inspiration to solve problems for Kant. In particular, a common objection to Kant is that his theory collapses unless we have some way to rule out self-serving maxims like “All rational agents do what they think Daniel Kokotajlo wants them to do.” But how can we exclude these maxims in a non-ad-hoc way that also avoids undermining Kant’s justification for obeying the Categorical Imperative in the first place?

Cyberkant has a ready answer to this problem: It’s a fact that if I help other rational agents in need, other rational agents will help me in need. But it’s not a fact that if I help other rational agents named Daniel and ignore the rest, other rational agents will also help other rational agents named Daniel and ignore the rest. Why is the first If-then claim a fact and the other one not? Because that’s how our minds are structured; it’s a fact we know about the world. (11)

7. Conclusion

This paper is, admittedly, rather speculative. However, I think that the similarities highlighted here are intriguing enough to motivate further investigation. Even though Kant and Cyberkant are doubtless very different, they might be able to learn some things from each other. (12)

8. Endnotes

  1. This is a sci-fi novel by Charlie Stross about a slow takeoff distributed technological singularity. The full text is free online at There are different ways to interpret the quote, but my preferred interpretation will soon be clear.
  2. Another version: “Act as if the maxim of your action were to become through your will a universal law.” (421) This formulation is good for my purposes because, as we shall see, there is a sense in which your action does become a universal law, and decision-theoretic reasons to think that you should act accordingly.
  3. I’m not sure the formal epistemology treatment will be able to match the additional meaning of end-in-itself that Kant seems to have, the meaning by which there are certain things you can’t do to somebody even if they & everyone else in the entire world wishes it to be done. That said, it’s not out of the question to interpret Kant as primarily concerned with the adopt-their-ends-as-your own version of this imperative, and thinking of everything else as derivative. This is the interpretation Geoff Sayre-McCord teaches his undergrads, for example, and I find textual support for it in 429 where Kant explains that each rational creature thinks of his own existence as an end–perhaps this is why everyone’s existence should be treated as an end.
  4. Arguably evidential decision theory–the second-most-popular decision theory–thinks this way, though perhaps only as a special case of something even more general. Drescher, Soares & Fallenstein, and Oesterheld think this way. Doug Hofstadter and Chris Meacham seem attracted to it too. For Hofstadter, see For the others, see the References.
  5. This is where the “Cyber” in the title comes from.
  6. Agents could reason using backwards induction: The most powerful won’t cooperate with anyone less powerful, and so the second-most powerful won’t cooperate with anyone less-powerful either, and so… everything falls apart.
  7. For example, say there are 100 levels and the people on the top and bottom know it, but everyone else is clueless about their position. Each of the 98 people in the middle will reason: If I be nice to people less powerful than me, then all the people (except for the guy on top) will be nice to me, and so (unless I’m near the top, which is unlikely) I’ll benefit.
  8. The game theory literature is full of reasons why being able to self-bind is useful. The decision theory literature has talked about this, too. (Meacham 2010)
  9. Saves having to pay those binding costs.
  10. This is true for standard measures of accuracy like the Brier score.
  11. Originally I thought that Kant could straightforwardly solve the problem by engaging in a regress: In order to choose “Everyone does what Daniel wants” as my maxim, I’d have to first set myself the goal of finding a self-serving maxim, and that would not be universalizeable. However, it’s not strictly speaking true that I’d have to do that. We can imagine a possible world in which I choose “Everyone does what Daniel wants” as my maxim not via malice but out of some other motive or perhaps no motive at all, and in that world Kant would need to say that my action satisfied the Categorical Imperative.
  12. Many thanks to Markus Kohl, Karl Adam, and Krasimira Filcheva for helpful discussion.

9. References

Bostrom, N. (2003) “Are you living in a computer simulation?” Philosophical Quarterly, Vol. 53, No. 211, pp. 243-255.

Drescher, G. (2006) Good and Real. MIT Press.

Kant, I. (1781) Critique of Pure Reason. Guyer and Wood translation. Cambridge University Press, 1998.

Kant, I. (1785) Grounding for the Metaphysics of Morals. J. Ellington translation. Hackett publishing company 1993.

Meacham, C. (2010)“Binding and its Consequences” Philosophical Studies, 149(1): 49–71, 2010.

Oesterheld, C. (2017) “Multiverse-wide Cooperation via Correlated Decision Making.” Unpublished. Available online at

Soares, N. and Fallenstein, B. (2015) “Toward Idealized Decision Theory” arXiv: 1507.01986, 2015.

Strevens, M. (1999) Objective probability as a guide to the world. Philosophical Studies 95: 243-275.

Tomasik, B. (2015) “Interpreting the Categorical Imperative.” Blog post. Available online at:

Williams, G. (2018) “Kant’s Account of Reason”, The Stanford Encyclopedia of Philosophy (Summer 2018 Edition), Edward N. Zalta (ed.), forthcoming URL = <>.

Five minutes on whether the industrial revolution was a high-leverage time

In this excellent post, Ben Garfinkel asks:

An analogy is sometimes made to the industrial revolution and the agricultural revolution. The idea is that in the future, impacts of AI may be substantial enough that there will be changes that are comparable to these two revolutionary periods throughout history.
The issue here, though, is that it’s not really clear that either of these periods actually were periods of especially high leverage. If you were, say, an Englishman in 1780, and trying to figure out how to make this industry thing go well in a way that would have a lasting and foreseeable impact on the world today, it’s really not clear you could have done all that much. 

I figured it would be worth spending five minutes thinking about whether it would be reasonable for a smart, wealthy, effective-altruist Englishman in 1780 to focus on trying to steer the long-term future via influencing the industrial revolution.

  1. It should have been clear to our hypothetical Englishman that the industrial revolution would lead to an increase in economic power that would result in an increase in military power. Thus, he might have been able to predict that the colonialism sweeping the globe would intensify thanks to the IR. He could influence this by bringing the IR to other countries directly, rather than waiting for the British Empire to get even bigger and more powerful. (For example: Bringing steam engine technology to China or Japan would probably work decently well at preventing them from getting colonized.) If for whatever reason he decided that British colonization was a good thing, he could have sped it up by sabotaging the IR as it spread to other countries (France, etc.)
  2. On the subject of speeding up and slowing down, he could have done research on the likely effects of such increased worker productivity on society–would it lead to a higher or lower standard of living? He could then have agitated with the British government to accelerate or slow down the IR. (For example, he might reasonably conclude that the IR would render slave plantations obsolete, and thus make abolishing slavery easier. Or he might conclude instead that factory labor is particularly suitable to slavery. I don’t myself know which is right, but that’s because I don’t know history that well; living through it perhaps our Englishman could have made some decent guesses at least.)
  3. Miscellaneous: He could have tried to influence whether the IR is publicly associated with conservatism or progressivism or monarchism or whatever, or whether it is seen as politically neutral. He could have tried to anticipate the problems it would cause (pollution, urbanization, plagues) and begin working on solutions early.

OK, out of time & ideas. (That was more like 10 minutes). What, if anything, to conclude?

I think it’s plausible that a smart, wealthy Englishman in 1780 would have had a decent amount of leverage on the future via the IR–but also plausible that he would have had even more leverage via sociopolitical things like advocating for democracy, or slavery abolition, or decolonialism, or whatnot. And it’s also plausible that he would have had even more leverage by advancing the scientific method, especially in medicine.

I’m not sure what to make of this, if anything. I think there is a big disanalogy between AI safety stuff and the IR, namely, that there seems to be a real risk of AI takeover existential risk, whereas there was no such thing for the IR. For the IR, the biggest points of leverage were over how fast it happened and over where it happened. For AI, those points of leverage exist also, but there is also a much bigger and more important lever having to do with whether or not we all die.

I think I would very seriously consider abandoning my focus on AI if I were convinced that AI wasn’t an existential threat. If, for example, the control problem were solved, so that I was confident AI would be merely like a second IR, then I would maybe shift to more sociopolitical activism, trying to change social structures to better prepare for AI (or to distribute it more equitably).

Mozi, Mengzi, and Effective Altruism

[Author’s note: Another old paper makes it online!]

A while back I took a class on ancient chinese philosophy, taught by David Wong (who is great, by the way.) One of the things that Professor Wong noted was the similarity between modern-day ethical debates surrounding effective altruism and the ancient dispute between Mozi and Mengzi. I dug a little deeper and made a list of all the similarities I could think of; this is that list. Comments welcome:

I’m sufficiently impressed by these similarities that I think it is fair to say that Mozi and Mengzi really were talking about the same issues that feature prominently in debates about EA today; they were even making many of the same arguments and taking many of the same positions. I think this is really cool. If I ever teach intro to philosophy (or ancient philosophy, or non-western philosophy, or intro to ethics) in university, I intend to include a section on Mozi/Mengzi/EA.

An analogy for the simulation argument

To people already familiar with the argument, this may be old news. It’s an analogy to help people feel the intuitive force of the argument.

Suppose the following: New diseases appear inside people all the time. Only one in ten diseases is contagious, but the contagious diseases spread to a thousand other people, on average, before dying out. The non-contagious ones don’t spread to anyone else. You get sick. You haven’t yet gone to the doctor or googled your symptoms; given the above facts, part of you wonders whether you should bother… after all, 90% of diseases only ever infect one person. So, how likely is it that someone else has had your disease before?

Draw a Venn diagram with two circles: “First victim” and “contagious.” This makes three interesting categories:

A = First victims of noncontagious diseases

B = First victims of contagious diseases

C = Nonfirst victims of contagious diseases

 Since only one in ten diseases is contagious, B/A = 1/9.Since contagious diseases spread to a thousand people on average, B/C is 1/1000. It follows that C/(A+B+C) = 100/101.

Since you know you are diseased, you should assign credence to each hypothesis “I’m in A” “I’m in B” “I’m in C” equal to the fraction of diseased people who are in that category, at least until you get evidence that you would be more likely to get in one category than another.

(For example, if you google your symptoms and get zero hits, that’s evidence that is more likely to happen to people in group A or B, so you should update to be less confident that you are in group C than the base rate would suggest.)

So you are almost certain to be in category C, since they make up 100/101 of the total population of diseased people, and at the moment you don’t have any evidence that is less likely to happen to people in category C than people in the other categories. So it’s almost certain that other people have had your disease already, even though 90% of diseases only ever infect one person.

In the simulation argument, the reasoning is similar.

Suppose that 90% of non-simulated civilizations never create ancestor sims, but that the remaining 10% create 1000 each on average. Then most civilizations are ancestor-simulated.

Do we have any evidence that is more likely to happen to people who are ancestor-simulated than people who are not, or vice versa?

You might think the answer is yes: For example, simulated people are more likely to see things that appear to break the laws of physics, more likely to see pop-up windows saying “you are in a simulation,” etc. 

But Bostrom anticipates this when he restricts his argument to ancestor simulations. Ancestor simulations are designed to perfectly mimic real history, so the answer is no: Someone in category C is just as likely to see what we see as someone in category B or A.

So even if we rule out non-ancestor-simulations entirely, the argument goes through: Most civilizations with evidence like ours are ancestor-simulated, and we don’t have any reason to think we are special, so we are probably ancestor-simulated. And of course, we shouldn’t rule out non-ancestor-simulations entirely, so the probability that we are simulated should be even higher than the probability we are ancestor-simulated.

(Clarificatory caveat: Bostrom’s argument is NOT for the conclusion that we are in a simulation; rather, it is a triple-disjunct. In the framing discussed here, Bostrom leaves open the possibility that Group A is extremely large relative to Group B, large enough that it is bigger than B and C combined.)

Great Map of the Mind

We have all these theories and debates about parts of the mind; why not make a big map to show how they all fit together? 

Obviously, minds aren’t all the same. But having a map like this helps us organize our thoughts, to better understand our own minds and the minds we are trying to design and reason about. I’d love to see better versions, or elaborations of this one, or entirely different mind-designs.

If you want the original document: Get, then follow this link and click “Open with…” and then select I’d love it if people spin off improved versions.

Not Your Grandma’s Phenomenal Idealism

[Author’s note: Now that I’m finally putting my stuff online, I have a backlog to get through. This is a term paper I wrote three years ago. As such, it reflects my views then, not necessarily now, and also it is optimized for being a term paper in a philosophy class rather than an academic paper for an interdisciplinary or AI-safety audience. Sections I and II sketch a theory, Lewisian Phenomenal Idealism, which is relevant to consciousness, embedded agency, and the building-phenomenal-bridges problem. The remaining sections defend it against objections that you may not find plausible anyway, so feel free to ignore them. Here is the gdoc version if you want to give detailed comments or see the footnotes.]

Not Your Grandma’s Phenomenal Idealism

[T]he structure of this physical world consistently moved farther and farther away from the world of sense and lost its former anthropomorphic character …. Thus the physical world has become progressively more and more abstract; purely formal mathematical operations play a growing part.  —Max Planck

When you see something that is technically sweet, you go ahead and do it and argue about what to do about it only after you’ve had your technical success. That is the way it was with the atomic bomb.  —Robert Oppenheimer

It started as just a weird theory invented to serve as a counterexample, but now I’m halfway convinced that it’s true.  —Daniel Kokotajlo

In the second chapter of his forthcoming book, “Idealism and the limits of conceptual representation,” Thomas Hofweber argues that phenomenal idealism is not worth taking seriously, on the grounds that it conflicts with what we know to be true—for example, we know that there were planets and rocks before there were any minds. (p12) I think this is too harsh: While we may have good reasons to reject phenomenal idealism, geology isn’t one of them. I think that phenomenal idealism should be taken as seriously as any other weird philosophical doctrine: The arguments for and against it must all be considered and balanced against one another. I don’t think that empirical considerations, like the deliverances of geology, have any significant bearing on the matter. The goal of this paper is to explain why.

I will begin by locating phenomenal idealism on a spectrum of other views, including reductive physicalism, which I take to be the main alternative. I will then present my own version of phenomenal idealism—“Lewisian Phenomenal Idealism,” or LPI for short—which I argue neatly avoids most of the standard objections to phenomenal idealism. It’s a proof of concept, so to speak, that phenomenal idealism is worth taking seriously. Finally, and most importantly, I’ll defend LPI against the strongest objection to it, the objection that it illegitimately reassigns the referents of the terms in the sentences we know to be true, and hence conflicts with what we know to be true.

I: Lewisian Phenomenal Idealism

Hofweber’s definition of phenomenal idealism is as follows:

The immediate objects of perception are thus phenomena, mental things which we are directly aware of. So far this is just a view about perception. But what turns it into idealism is to add that the objects are or are constructed from these phenomena, somehow. The material world is not a mind-independent world that we see indirectly, via the phenomena, nor is it represented by the phenomena. Instead, the phenomenal world is the material world. The phenomena do not represent the objects, but constitute them. (p20)

Though Hofweber’s definition above commits phenomenal idealism to two theses—one about perception, and another about ontology—I will only focus on the latter, since it generally taken to be more central. The phenomenal idealist position that I aim to defend is a version of the “Reductive Phenomenal Idealism” on the following spectrum:

    • Eliminative Physicalism: There are physical objects, but no minds or experiences.
    • Reductive physicalism: There are both, but only physical objects are fundamental: Minds and experiences are constituted by physical objects.
    • Dualism: There are both fundamental physical objects and fundamental minds and experiences.
    • Reductive Phenomenal Idealism: There are both, but only minds/experiences are fundamental: Physical objects are constituted by minds and experiences.
    • Eliminative Phenomenal Idealism: There are minds and experiences, but no physical objects.

Based on Hofweber’s definition and on that given by Foster (a contemporary defender of phenomenal idealism) it is fair to characterize Phenomenal Idealism for our purposes as just Reductive Phenomenal Idealism above. I located it on this spectrum to highlight the parallel between reductive phenomenal idealism and the reductive physicalism that we all know and love: At least at first glance, they both posit the same entities, and the same number of fundamental ontological kinds; the only difference is the direction of fundamentality.

Lewisian Phenomenal Idealism (LPI) has four components: An ontological claim, a philosophy of science claim, an empirical claim, and a revisionary reductive analysis of our talk about physical objects. It will take a while to explain each of them in sufficient detail:

LPI Ontology: Fundamentally, there are only minds and experiences.

I intend to avoid the issue of how minds and experiences are related—are they two separate kinds? Is one a property or relation of the other? It should be irrelevant for the purpose of this paper.

LPI Philosophy of Science: Laws of Nature are as David Lewis’ Best Systems Theory says: They are the theorems of the deductive system that describes the world with the best balance of simplicity, strength, and fit. (Lewis 1980)

This requires a bit of explanation. The idea is that which minds exist, and which sequences of experiences they have, can be described by a variety of deductive systems. Some are very detailed, accurately describing everything there is to describe, but are very complex; others are rather simple, but miss out on a few details. The best system is the hypothetical system that achieves the best balance of simplicity, strength, and fit. The Laws of Nature, then, are defined in terms of the best system. Lewis says they are the theorems of the best system; I’ll eventually go for something a little more nuanced, but that will do for now.

The Best Systems account of lawhood is controversial, but I’m happy to accept the consequences for now. If the worst that can be said of LPI is that it relies on Lewis’ theory of lawhood, this paper is a success.

LPI Empirical Claim: The Best System is of the following form: For each structure of type M in the theorems of [insert physicalist Best System here] passing through a sequence of states S1,…Sn, there exists a mind which has the sequence of experiences given by f(S1),…f(Sn).

This requires quite a lot of explanation. I’ll start by explaining what a physicalist Best System would look like, given what we know of physics. It would have some description of which objects in which relations exist in the initial condition, and then some description of how the system evolves over time. Both descriptions would be heavily constituted by the deliverances of ideal physics. It is this description, this Best System, that LPI places in the brackets above. Importantly, I described things this way for convenience only. LPI does not parasitically depend on physicalism; I put it that way for ease of exposition and to highlight the similarities between the two theories. Technically LPI would have [insert description of initial conditions and rules for how they evolve over time]; the idea is that whatever evidence physics gives us, according to physicalism, for the rules and conditions of the Best System is, according to LPI, evidence instead for the rules and conditions of the bracketed section of the Best System.

Now, reductive physicalism follows up its account of the Best System with a revisionary reductive analysis of mind/experiences, so that the theory as a whole can posit minds and experiences as well as fundamental physical objects. This reductive analysis is supposed to be partially the result of philosophy (armchair theorizing about what sorts of functional, behavioral, or structural properties a system must have in order to count as a mind) and partially the result of psychology (empirical data on which neurochemical structures lead to which experiences under which conditions). Never mind the details, the point is that according to reductive physicalism there is some type M such that a mind exists whenever there is a physical structure of type M. According to LPI, then, there is some type M such that a mind exists whenever in the bracketed section of the Best System there is a structure of type M. Something similar can be said about the function f. Whereas according to reductive physicalism, philosophy and psychology tell us how minds and experiences supervene on physical structures, according to LPI, philosophy and psychology tell us about sections of the Best System which describes which minds/experiences there are.

One important difference between LPI and reductive physicalism is that for reductive physicalism, all this stuff about minds and experiences is part of a revisionary reductive analysis, separate from the Best System for describing the world; by contrast, for LPI, this is all part of the Best System. More on this point in Section II.

LPI Reductive Analysis: Our talk about physical objects is analyzed as talk about the bracketed section of the Best System. Our talk about the Laws of Nature that the sciences discover is analyzed as talk about the bracketed section as well. Indeed for convenience we can think of the bracketed section as being a “simulation” of the world that the physicalist thinks is actual. Most ordinary conversation is analyzed as talk about the simulation.

I’ll supplement this with two examples: When a physicist says “We just discovered that there are exactly 13 kinds of fundamental particle,” their claim can be analyzed as “We just discovered that the part of the Best System which simulates a bunch of fundamental particles, simulates exactly 13 kinds.” When an atheist geologist says “There were rocks and planets for billions of years before there were minds,” their claim can be analyzed as “The part of the Best System which simulates a bunch of objects evolving over time, simulates rocks and planets billions of simulation-years before it simulates objects of type M.”

II: Discussion

Before moving on to Hofweber’s criticism of phenomenal idealism, it is worth taking the time to discuss a few issues that arise independently.

First, LPI may strike some readers as extremely suspicious. Isn’t it ad hoc? Doesn’t it basically steal all the achievements of reductive physicalism and claim them as its own? It seems like an accommodation, rather than a prediction, of the data.

I have three responses to this worry. The first is that there is nothing wrong with stealing the achievements of a successful theory, if all that means is making a new theory that combines the same predictive accuracy with additional desirable traits. Indeed in most cases when this happens, all the reasons we had for believing the old theory transfer over into reasons to believe the new theory. This is, in general, how human knowledge progresses.

My second point is a warning not to overstate the successes of reductive physicalism. Physics has been successful; geology has been successful; psychology and neuroscience have been successful, etc. But they would have been equally successful if LPI and not reductive physicalism had been the dominant ideology for the past two centuries.

My final point is that the empirical claim LPI makes actually flows fairly naturally from the Ontological and Philosophy of Science claims it makes. Our minds are extremely complex. If the Best System describing minds/experiences did so directly, by specifying which experiences were had, in which order, it would have to be similarly complex. Arguably this Best System would be more complex than the one posited by LPI’s Empirical Claim! By describing minds/experiences indirectly, by simulating a large physical universe that evolves according to simple laws, and then extracting descriptions of minds and experiences from that simulation, the Best System can compress the data significantly. Hence, arguably, LPI Empirical Claim is actually predicted by the conjunction of Occam’s Razor, the datum that complex minds exist, and the ontological and philosophy of science claims made by LPI. This puts LPI on the same footing as physicalism with respect to predicting the world as we find it.

All that being said, LPI is admittedly more complex than reductive physicalism. However complicated the Best System is according to reductive physicalism, the Best System according to LPI will be that and then some. (The additional complexity will be approximately the sum of the complexity of Type M and the complexity of the function f.) So, other things equal, by Occam’s Razor we ought to prefer reductive physicalism to LPI.

Other things are not equal. There are arguments against reductive physicalism, which, if successful, rule it out before Occam’s Razor can be brought to bear. These are the arguments that have occupied the literature on consciousness for decades and possibly centuries: the “explanatory gap,” the zombie thought experiment, the Mary’s Room case, etc.  I am not trying to say that these arguments are correct; my point is just that LPI can’t be ruled out straightaway by Occam’s Razor. The arguments must be considered first.

Finally, I suspect that LPI may solve many of the problems in philosophy of mind. It seems to provide a non-arbitrary connection between the mental and the physical, and explains how that connection holds. It accounts for our intuitions about qualia, the unity of consciousness, etc. It resolves worries about vagueness and borderline cases of consciousness/personhood. It even suggests a principled answer to questions about the persistence of personal identity over time! It does this in the same way that dualism does it—by positing fundamental minds/experiences subject to contingent laws. Questions about minds and experiences become normal empirical questions, no more mysterious than questions about the gravitational constant or the composition of water. Unlike dualism, though, LPI doesn’t run into problems trying to connect mind and matter—there is no overdetermination, no causal inaccessibility, etc.

I should qualify the above by saying that I haven’t worked out the implications of LPI in any detail yet; I may be wrong about its advantages. My point in mentioning these speculative ideas is to garner support for the thesis of this paper, which is that LPI—and by extension, phenomenal idealism more generally—shouldn’t be ruled out straightaway as conflicting with what we know to be true. On the contrary, it’s an interesting philosophical theory that deserves proper philosophical consideration. In the next three sections, I’ll lay out and discuss Hofweber’s arguments against this thesis.

III: The Coherence Constraint

In this section I will lay out Hofweber’s argument against phenomenal idealism in detail. According to my categorization, he has four arguments for why phenomenal idealism conflicts with what we know to be true. They aren’t meant to all apply at the same time; different arguments apply to different versions of phenomenal idealism. In this section I will show that LPI avoids the first three arguments. The remaining argument, which I take to be the most important, will occupy the rest of the paper.

Hofweber’s arguments revolve around the Coherence Constraint:

Coherence Constraint: An acceptable form of idealism must be coherent with what we generally take ourselves to know to be true. (p12)

Presumably the Coherence Constraint is to be generalized to all metaphysical theories, not just idealism. A helpful gloss on it follows:

To accept the coherence constraint is closely tied to thinking of metaphysics as being modest with respect to other authoritative domains of inquiry. Although any scientific result might be mistaken after all, metaphysics should not require for its work that this turns out to be so. It should do something over and above what other authoritative parts of inquiry do. It asks questions whose answer is not given by and not immediately implied by the results of the mature sciences. Applying this to idealism it means that idealism must be compatible with us living on a small planet in a galaxy among many. It must be compatible with our having a material body in a material world, and so on. It can make proposal about what matter is, metaphysically, or other things, but whatever it is supposed to be, it must be compatible with and coherent with the rest. This is the coherence constraint, and any form of idealism worth taking seriously must meet it. (p12)

I’ll have a lot to say about this in the next two sections. For now, I’ll briefly discuss how LPI avoids the first three arguments:

Argument One: Problem of Intersubjectivity

The idea behind this problem is that one of the things we know to be true is that there are other minds like us, and that their experiences are coordinated with ours—when I type the word “Porcupine” on my screen, I know that eventually someone (In this case Hofweber himself) will see the word “Porcupine” on his. On theistic versions of phenomenal idealism, this can easily be explained: God coordinates everyone’s experiences so that they match up in this way. But LPI is not theistic; can it explain how all our experiences are coordinated?

Yes it can. The Laws which govern minds and experiences involve a “simulation” of physical objects, and which minds there are and which experiences they have are determined by this simulation. If minds had uncoordinated experiences, the laws governing them would not be of the form specified by LPI Empirical Claim, and indeed would probably be much more complicated.

There is a legitimate worry about how LPI can explain the coordination of our experiences by reference to these Laws, since the Best System in which they are based is merely a description of which minds there are and which experiences they have. However this worry is a general problem with Lewisian accounts of lawhood, and not a problem with LPI in particular.

Argument Two: Problem of Unobserved Objects

The idea behind this problem is that one of the things we know to be true is that there were rocks and planets before there were minds—geology and astronomy have discovered this, at least if we assume atheism is true and there are no parallel universes with aliens in them etc. More generally, it seems like one of the things we know to be true is that there are objects which have not, are not, and never will be observed by any mind. How does LPI account for this fact?

It does so with its revisionary reductive analysis of objects. Talk about physical objects is analyzed as talk about structures in the simulation. When an atheist geologist says “There were rocks and planets for billions of years before there were minds,” their claim is analyzed as “The part of the Best System which simulates a bunch of objects evolving over time, simulates rocks and planets billions of simulation-years before it simulates objects of type M.” When an atheist physicist says “There are objects which have not, are not, and never will be observed by any mind” their claim is analyzed as “In the simulation, there are objects which never get observed by any mind.”

In general, LPI marks as true all the same sentences that ordinary physicalism marks as true—sentences like “There were rocks before there were minds,” “Some objects never get observed,” “There is a computer in front of me right now,” etc. Of course, LPI achieves this only by changing the referents of the relevant sentences: instead of referring to external, mind-independent objects, they refer to structures in a simulation, which is itself a component of the Best System for describing which minds/experiences there are. This is exactly what one should expect; of course a reductive phenomenal idealist theory is going to say that our talk about physical objects does not refer to external, mind-independent things, since reductive phenomenal idealism by definition says that physical objects are reduced to mind-dependent things. Other reductive phenomenal idealist theories reduced physical objects to counterfactual experiences, or possible experiences; LPI does something different, but similar in kind.

Nevertheless you might think that this changing-of-the-referents, this reductive analysis, is illegitimate. This is precisely the move made by Argument Four, and responding to it will occupy Sections IV and V of this paper.

Argument Three: Not Really Phenomenal Idealism

At various points in his book, Hofweber considers versions of phenomenal idealism that perhaps escape his criticisms—except that they do so at the cost of their phenomenal idealist credentials. One example is a version of pantheism, which says that physical objects are aspects of god—in particular, ideas in God’s mind. (p24) In this case, Hofweber says, physical objects inhabit a world that is independent of our minds at least, even though it might not be independent of all minds. It isn’t physicalism, but it isn’t phenomenal idealism either. Perhaps LPI has done the same; perhaps it avoids Hofweber’s arguments against phenomenal idealism because it is not really phenomenal idealism.

This argument is one of the reasons that I decided to build LPI around a Lewisian conception of lawhood. I can see how, arguably, if laws were self-sufficient entities in some sense, one might say that the “simulation” is really a mind-independent external reality. But since according to LPI physical objects are just structures in the simulation, and the simulation is just a part of the Best System, and the Best System is just a description of which minds there are and which experiences they have, physical objects really are mind-dependent according to LPI. And they are dependent on minds like ours, since minds like ours are the only minds there are.

IV: The No Reinterpretations Objection

The No Reinterpretations Objection revives the Problem of Unobserved Objects by rejecting LPI’s revisionary reductive analysis of our talk about physical objects:

The idealist must meet the coherence constraint by making clear that what their view is is coherent with what we know to be true. It is not enough to do this to assign some meaning to the words ‘there were dinosaurs’ and show that with this meaning it is compatible with idealism that ‘there were dinosaurs’ is true. Instead, the idealist must show that the statement is compatible with idealism with the meaning it in fact has, i.e. they must show that there were dinosaurs (before there were humans) is compatible with idealism. As such the idealists proposal about the meaning of `there were dinosaurs’ must be taken as an empirical proposal about the actual meaning of this sentence in English. It is one thing to show that idealism is compatible with the truth of this sentence given some assignment of meaning to this sentence, and quite another to show it is compatible with the truth of the sentence with the actual meaning of it. (p26)

As I understand it, Hofweber is objecting to the “Revisionary” part of LPI’s revisionary reductive analysis. He thinks that statements about physical objects only cohere with LPI if they do so given the meanings that they in fact have, in English. It doesn’t count if they cohere with LPI given different meanings supplied by LPI. On the face of it, this objection is very plausible. Any set of sentences can be made coherent with any other set of sentences, if you are allowed to change the meanings of the sentences! It seems that LPI is helping itself to a technique—revisionary reductive analysis—that will allow it to get away with anything.

In this section, I will respond to this basic version of the No Reinterpretations objection. I’ll argue that, in fact, the burden of proof is on Hofweber to go beyond what has been said so far and present a positive argument for the illegitimacy of LPI’s revisionary analysis. In the next section, I’ll examine a later argument Hofweber makes that I construe as an attempt to meet that burden.

I’ll begin by pointing out a tension between endorsing the Coherence Constraint and critiquing LPI in this way. In his elaboration quoted above, Hofweber explicitly permits idealism to “say what matter is, metaphysically.” (p12) Thus Hofweber agrees there is some legitimate middle ground between the bad kinds of revisionary analysis and mere proposals about the English meanings of words. My point so far is that it is unclear where the boundary is; in the remainder of this section, I’ll argue that LPI occupies that acceptable middle ground.

Consideration One:

My first point is that revisionary reductive analysis is a legitimate philosophical and scientific move that has been made successfully many times in the past, and is often attempted today. I’ll give three examples, but many more could be generated if necessary:

    • Laws Example: Laws of Nature were once taken more literally, as decrees of God, or at least descriptions of His governance of creation. At some point the scientific community switched to a new concept that didn’t necessitate a Lawgiver.
    • Relativity Example: Space and time are intuitively thought of as distinct; even among most normal English speakers today, it is fair to say that space means Euclidian space and time means something else. Yet according to relativity, there is no such space and no such time in the actual world.
    • Physicalism Example: Minds were for the longest time thought to be essentially immaterial and unified. This was no “folk” belief either—the best scientists and philosophers of the modern era thought this. Reductive physicalism eventually came along and overturned this view, saying that minds are neither immaterial nor unified.

I think that the Physicalism example is particularly close to what LPI is trying to do: Recalling the physicalism-dualism-idealism spectrum, LPI is advocating that we revise our understanding of the world in the same way that Physicalism did, only in the opposite direction.

I hold these up as examples of revisionary analysis, but this can be disputed. For example, one might say instead that the meaning of “minds” stayed the same, because it was never committed to immateriality and unity in the first place. Rather, “minds” meant something like “That in virtue of which things can think, feel, and choose” or perhaps “The relevant cause of my ‘mind’ mental representation tokens.”

I’m happy to accept this possibility, because if we can convince ourselves that the meaning of our words was preserved in the examples given, i.e. if we can convince ourselves that they aren’t really examples of revisionary analyses, then we should also be able to convince ourselves that LPI isn’t really performing a revisionary analysis either. Whatever it is that Physicalism did when it convinced people that minds weren’t really immaterial unities—I claim that LPI is trying to do the same thing, but in the opposite direction.

It’s worth mentioning a point made by Foster and Smithson: Often when people adopt a radical change in their ontological beliefs, they initially express the change by saying “I now believe that there is no X!” yet then soon after start saying “I still believe there is X, but it isn’t what I used to think it was.” (Foster 1994, Smithson 2015) I remember some of my teachers saying things like this in middle school, when we learned about how material objects are “mostly empty space,” and about how they “never actually touch each other,” etc. Presumably the same thing happened with the examples given above, and presumably the same thing would happen again if we started believing in LPI. I take this as evidence that the sort of thing LPI is doing is closer to “say[ing] what matter is, metaphysically” than to “conflicting with what we know to be true.” (Hofweber p12) It is evidence that our cherished knowledge of physical objects is not knowledge that there are physical-objects-as-physicalists-define-them, but rather knowledge that there are physical objects-according-to-some-broader-definition.

Consideration Two: The rough idea here is that we want our epistemology to be reasonably open to change, so that we can converge on the truth from a wide variety of starting points. We don’t want which beliefs are permissible to depend on non-truth-tracking historical accidents. To illustrate:

LPI Takeover Case: Suppose that I convert some wealthy donors to belief in LPI, and we engage in a decades-long covert proselytization process in which we change the way young scientists are taught to think about physical objects. We get the textbooks changed to use definitions of “object” that are neutral between the LPI definition and the physicalist definition, etc. In other words, we change the meaning of the term “object” in English, so that it is more permissive. Once we have accomplished this, we introduce LPI into the philosophical discourse, confident that it now passes the Coherence Constraint.

Clearly something has gone wrong here. Yet this is, I claim, relevantly similar to what happened with reductive physicalism. Not that there was a conspiracy or anything; just that the meanings of our terms shifted over time, in a way that allowed for the possibility of reductive physicalism, but not in a way that particularly tracked the truth—it’s not like the meanings of our terms shifted because we found empirical evidence that reductive physicalism (as opposed to dualism) was true. Perhaps the shift was motivated by philosophical considerations; people became dissatisfied with dualism as an explanation for mental causation, etc. But in that case, the conclusion should be that the shift in meaning in the LPI Takeover Case is legitimate if there are good philosophical reasons motivating it. And if that’s the case, then we can’t yet rule out LPI as conflicting with what we know to be true, because we have to consider the philosophical arguments for and against it first. And that’s precisely the thesis of this paper.

Consideration Three: Contemporary analytic philosophy is full of attempted revisionary analyses. Philosophers debate definitions of objective chance, universals, mathematical objects, composite objects, vague objects, etc. and they debate whether or not these things exist, and if so, under what definition. Sometimes attention is paid to the actual English meanings of our terms, but often it is not. One hears things like “There are no chairs, only particles arranged chair-wise,” and “There aren’t really any numbers; they are just convenient fictions.” These are examples of the english meanings being kept but the associated knowledge claims rejected. The examples I gave earlier are examples of the opposite strategy. Thus, LPI is very much situated within a broader tradition; what it is doing is normal and accepted.

Maintaining his consistency, Hofweber goes on to explicitly reject some of the attempts I mention above—specifically, nominalism in mathematics and eliminativism about ordinary objects. (Chapter 7) His rejection of LPI’s revisionary analysis is part of a broader rejection of a whole class of similar analyses in contemporary analytic philosophy.

In the next section I will evaluate his argument for this; for now I stick to the more moderate conclusion—which I take to have established by now—that the burden of proof is on Hofweber: In the absence of a good positive argument against the legitimacy of LPI’s revisionary analysis, we ought to accord it the same legitimacy as all the other historically successful and currently accepted attempts at revisionary analysis. This doesn’t mean we should accept LPI, of course—it just means that LPI should be accepted or rejected on the basis of all the arguments for and against it, and not simply rejected as conflicting with what we know to be true.

V: The Argument Against Reinterpretation

Elsewhere in his book (Chapter 7), Hofweber presents an argument for the existence of ordinary composite objects and against certain views in mereology, which probably count as “Eliminative Physicalism” under my classification.  I believe this argument can be generalized to apply to the case of LPI as well. In this section I’ll first lay out the argument as I construe it, and then attempt to poke three holes in it.

Hofweber’s Argument:

    1. (P1) Skepticism is false. (p251)
    2. (P2) If skepticism is false, then we are defeasibly entitled to the beliefs we form on the basis of perception. (p251)
    3. (L3) (From P1 & P2) We are defeasibly entitled to the beliefs we form on the basis of perception. (p251)
    4. (P4) Some of the beliefs we form on the basis of perception are incompatible with LPI. (p252)
    5. (L5) (From L3 and P4) So there are some beliefs which we are defeasibly entitled to, which are incompatible with LPI. (p252)
    6. (P6) If our entitlement to beliefs is defeated, it is either rebutted or undercut, and if it is undercut, either our entitlement to all perceptual beliefs is undercut or not. (p252)
    7. (P7) If our entitlement to all perceptual beliefs is undercut, then skepticism is true. (p253)
    8. (L8) (From P1 & P7) So it’s not the case that our entitlement to all perceptual beliefs is undercut. (p253)
    9. (P9) (With support from L8) Our entitlement to the beliefs mentioned in L5 (the ones that are incompatible with LPI) is not undercut. (p254)
    10. (P10) If our entitlement to those beliefs is not undercut, we have overwhelming empirical evidence for them. (p258)
    11. (L11) (From L5, P9, & P10) So there are beliefs formed on the basis of perception which are incompatible with LPI, which are not undercut, and which we have overwhelming empirical evidence for. (p257-261)
    12. (P12) Beliefs for which we have overwhelming empirical evidence cannot be rebutted. (p261-263)
    13. (C13) (From L3, L11 & P12) So there are beliefs incompatible with LPI, for which we have overwhelming empirical evidence, and we are entitled to those beliefs. (p263)

Since the original argument is about composite objects rather than mind-independent objects, I’ve had to modify a few of the premises. In particular, the relevant beliefs posited by P4 as incompatible with LPI are things like “There were rocks before there were humans,” and “I see a rock over there right now.” Crucially, terms like “rock” in these beliefs are supposed to be definitively incompatible with LPI. It’s not merely that terms like “rock” don’t mean “rock-structure in the LPI simulation;” they have to also not mean “whatever usually causes rock-appearances” or “the most natural existing referent for my use of the term ‘rock,’” or “something, I know not what, which I am justified in believing exists when I am appeared to rockly.” None of these meanings, even though they are neutral between physicalism and idealism, will do. P4 is saying that we form beliefs on the basis of perception which are not neutral between LPI and physicalism; rather, they are definitively incompatible with LPI.

I will accept P4, with qualifications: Given the above, these beliefs are probably not universally shared; many people probably form beliefs on the basis of perception that are weak enough to be compatible with LPI. Moreover, as Hofweber admits, (p254) these beliefs are contingent: If our culture, education system, and/or brain chemistry were different, we would instead form other, very similar beliefs that would allow us to function in all the same ways without being incompatible with LPI. Finally, LPI is far from alone as a theory which many people form perceptual beliefs against: Reductive physicalism and atheism, for example, are both theories which are incompatible with the perceptual beliefs of many (and perhaps even most) people.

The two premises I find problematic are the ones that Hofweber spends the most time justifying: P9 and P10. In the remainder of this section, I’ll lay out each of his arguments and explain why I don’t think they work.

Premise 9: (With support from L8) Our entitlement to the beliefs mentioned in L5 (the ones that are incompatible with LPI) is not undercut.

Hofweber says (and I agree) that the issue of undercutting in this case comes down to whether or not we have reason to think that the aforementioned beliefs track the truth. Hofweber considers an argument that (in the case of object composition, which his argument is geared towards) they don’t: In the possible world in which there are only simples arranged cup-wise, but no cup, we would still form the same perceptual beliefs in cups. So our belief in cups doesn’t track the truth of whether or not there are cups. (p254) Hofweber responds thus:

The counterfactual situation relevant to evaluate the counterfactual conditional about my cup not being there isn’t one where the simples are still there, but they somehow don’t compose a cup, but rather one where both the simples and the cup are gone. But then nothing would cause me to believe in a cup in front of me, and so my cup beliefs track the cup facts: all things being equal, I wouldn’t have that belief if there wasn’t a cup. (p255)

Converting this argument to work against LPI, Hofweber would presumably say that the beliefs we form on the basis of perception (and which are incompatible with LPI) track the truth, and that they do so because the relevant counterfactual in which they are false is the one in which e.g. we aren’t looking at anything that looks like a rock, geology finds human bones older than any rock, etc. In that counterfactual, we would not form those beliefs.

I am troubled by this reasoning. It seems to me that both counterfactuals are relevant; a belief can track the truth of some propositions but not others. It seems natural to say that our belief that there is a rock (in the LPI-incompatible sense) directly ahead is counterfactually able to distinguish between worlds in which there is a rock and worlds in which there is open space, but not between worlds in which there is a rock (in the LPI-incompatible sense) and worlds in which there is a rock (in the LPI-analysis sense). So, the thought goes, our belief is partially undercut—the part that has to do with the metaphysical nature of the rock is undercut, but the part that has to do with pretty much everything else, like what will happen if we kick the rock, how we can best avoid the rock, etc. is not. This would rescue LPI.

I expect Hofweber’s response to be that that way lies skepticism; we can extend that line of reasoning to the conclusion that all of our perceptual beliefs are systematically undercut, since there are worlds in which e.g. an evil demon is making us hallucinate everything. (p255)

I have two responses to this. The first is that we might be able to use “prior plausibility” to distinguish between the radical skeptical hypotheses and the non-radical, benignly skeptical hypotheses like LPI, mereological nihilism, and reductive physicalism. Presumably these latter hypotheses have more prior plausibility than the evil demon hypothesis. At any rate, in order to settle just how plausible these hypotheses are exactly, we have to consider the arguments for and against them. So if Hofweber’s argument that LPI shouldn’t be taken seriously depends on an assignment of low prior probability to LPI, then he is begging the question; he must instead first address the philosophical arguments for and against LPI, which is exactly the thesis of this paper.

My second response is that some of the examples I gave in Section IV seem to be similar enough to LPI that Hofweber’s argument here would work against them as well! I think any of them would do, but I’ll go with my favorite: Reductive physicalism. Most of the smartest philosophers and scientists in the 17th century formed beliefs on the basis of perception that were incompatible with reductive physicalism; for example, they thought that minds were immaterial and unified. They could use Hofweber’s argument to say that their beliefs track the truth: The relevant counterfactual in which their beliefs are false is one in which minds don’t even exist, not one in which minds exist but are somehow composed of material objects.

Similarly, one can imagine early scientists who thought of Laws of Nature as being given by a divine Lawgiver saying: “The relevant counterfactual in which there is no Lawgiver is a world in which everything moves about higgledy-piggledy; hence my belief in a Lawgiver on the basis of the regularity in the universe tracks the truth.” Indeed I have actually met people who argued this.

Given what I said in Section IV about how our beliefs oughtn’t depend on historical accidents (Consideration Two) I take these examples to be reductios of Hofweber’s argument.

Premise 10: If our entitlement to those beliefs is not undercut, we have overwhelming empirical evidence for them.

Hofweber takes himself to have established by this point that we have non-undercut entitlement to our beliefs about ordinary objects, but not to beliefs about mere simples arranged object-wise (since we don’t in fact have perceptual beliefs in such things). (p256) Converting this into talk about LPI, we may suppose that Hofweber has established by this point that we have non-undercut entitlement to our beliefs about mind-independent rocks, but not to our beliefs about more-broadly-defined-rocks, because we don’t in fact form the latter beliefs on the basis of perception.

Continuing to describe the converted argument rather than the actual one: Hofweber goes on to argue that this disanalogy compounds constantly into a tremendous empirical success for physicalism and predictive failure for LPI. LPI predicts that there are no mind-independent rocks in front of us; yet perception gives us non-undercut entitlement to believe that there are, every day. Even though LPI might in some sense predict our phenomenal experience just as well as the alternatives, it doesn’t predict certain crucial facts like the above.

As a result, Hofweber claims, science heavily disconfirms LPI: Our current scientific theories are defined using terminology that is inconsistent with LPI, and they are far more predictively accurate than their counterparts that would be defined using LPI’s revisionary analyses. (p261)

Hofweber goes on to say that, given the immense body of scientific and perceptual evidence against LPI, no amount of metaphysical argumentation should convince us that LPI is true. (p263) We can rule it out as conflicting with what we know to be true.

I find this argument problematic as well. It starts with a fairly innocuous premise about an asymmetry in our beliefs about two opposing theories, and ends up with a very strong and surprising conclusion. It smells suspiciously like the “Easy Knowledge/Bootstrapping” case described by Vogel and Cohen. Of course that isn’t a legitimate objection, so here are two:

My first objection is that Hofweber seems to be assuming a very strong form of scientific realism here.  Even if we set aside the anti-realists (though they constitute 11.6% of the professional population) the positions that remain, realism and structural realism, generally don’t say that we have overwhelming evidence for the literal truth of our current best theories. Rather, they say that we should accept them for now, while assigning high credence to the possibility that the truth is more nuanced and even that the central terms in our current best theories fail to refer. This caution is motivated by the history of science, which is a history of theory after well-confirmed theory turning out to be false when strictly and literally interpreted, even to the point where their central terms fail to refer. Granted, my worry here only applies to the scientific component of Hofweber’s argument, but I think it generalizes to the basic perceptual component as well. The history of strictly-literally-interpreted theories about ordinary observable objects mirrors the history of strictly-literally-interpreted scientific theories about unobservables.

My second objection is that the mere accumulation of truth-tracking, non-undercut perceptual beliefs does not by itself confer overwhelming evidence. Consider a doctor who examines a patient and comes to the perceptual belief, based on her years of experience, that the patient has a certain rare cancer. Suppose that the doctor knows her perceptions track the truth in cases like these: She gets the right answer 99% of the time. Does she have overwhelming evidence that the patient has the rare cancer? Does continuing to examine the patient again and again give her any more evidence?

The answer to both questions is no, if the cancer is sufficiently rare and if her repeated examinations are not independent. Suppose, as often happens, that the cancer strikes only one in every ten thousand patients, and that her repeated examinations are going to yield the same result, since they are based on the same perceived symptoms and intuitive judgments. Then no matter how many times the doctor examines the patient, her credence that the patient has the rare cancer should not rise above 0.01.

The moral of this story is that prior probabilities/base rates are crucial. Depending on how we like to put it, we can say either that priors are crucial for determining whether or not a reliable belief is undercut, or we can say that they are crucial for determining whether a non-undercut reliable belief constitutes overwhelming evidence. Either way, the lesson is that Hofweber needs to say something about LPI’s prior probability in order for his argument to work. But this will involve examining and engaging with the philosophical arguments for and against LPI, exactly as this paper urges.

VI: Conclusion

I admit that the arguments I have given do not conclusively defend LPI; phenomenal idealism may in fact turn out to violate the Coherence Constraint. This admission comes not from any particular weakness I have identified in my reasoning, but rather from a general worry that I don’t understand Hofweber’s: I’m not used to thinking in terms of entitlement, defeaters, and undercutting; my experience has more to do with credences, priors, and Bayesian updating.

Nevertheless, I think that the arguments presented here are more than strong enough to establish my modest conclusion: that LPI ought not be ruled out as conflicting with what we known to be true. On the contrary, it should be taken as seriously as any other weird philosophical theory, and the arguments for and against it should be explored. We should believe this until proven otherwise; the burden of proof is on Hofweber to do so, and he has not yet met it.


Foster, J. (1994) ‘In Defense of Phenomenalistic Idealism.’ Philosophy and Phenomenological Research, Vol. 54, No. 3. September. pp. 509-529

Goldman, A and Beddor, B. (2015) “Reliabilist Epistemology”, The Stanford Encyclopedia of Philosophy (Winter 2015 Edition), Edward N. Zalta (ed.), forthcoming URL = <;.

Hofweber, T. (2015) Idealism and the Limits of Conceptual Representation. Unpublished draft. The relevant chapters are 1, 2, and 7.

Hofweber, T. (2009) ‘Ambitious, Yet Modest, Metaphysics.’ In Chalmers, Manley & Wasserman (eds.), Metametaphysics: New Essays on the Foundations of Ontology. Oxford University Press 260—289

Ladyman, J. (1998) What is Structural Realism? (Studies in the History and Philosophy of Science vol 29 No 3, pp 409-424.

Lewis, D. (1994) Humean Supervenience Debugged. Mind, Vol. 103.412.

Lewis, D. (1980) A Subjectivist’s Guide to Objective Chance, in R. Jeffrey, ed., Studies in Inductive Logic and Probability, vol II. Berkeley: University of California.

Planck, M. (1996) ‘The Universe in the Light of Modern Physics’, in W. Schirmacher (ed.), German Essays on Science in the 20th Century (New York: Continuum), pp. 38–57.

Roberts, J. (2014) ‘Humean Laws and the Power to Explain.’ For UNC-Hebrew University workshop. Available online at

Stanford, K. (2001) ‘Refusing the Devil’s Bargain: What Kind of Underdetermination Should We Take Seriously?’ Philosophy of Science, Vol. 68, No. 3, Supplement: Proceedings of the 2000 Biennial Meeting of the Philosophy of Science Association. Part I: Contributed Papers (Sep., 2001), pp. S1-S12

Smithson, R. (2015) ‘Edenic Idealism.’ Unpublished draft.