Kripke's Argument for Dualism

1. It's possible for there to be mental states without brain states
2. Therefore, mental states are not identical to brain states

Since mental states (e.g. pain) and brain states (e.g. c fiber stimulation) are ridged designators—referring to the same object in every possible world—the inference from (1) to (2) is valid. Kripke thinks, and I want to agree, that at face value premise (1) seems to be true. And so the materialist, wanting to say that mental states reduce to brain states, is faced with the challenge of explaining away this intuition.

The materialist might meet Kripke's challenge by rallying behind other well established identity claims, considering them partners in crime. If we're not prepared to entertain doubts about, for example, water being identical to H2O, or lightening being identical to the discharge of electrons, or heat being identical to the excitement of molecular particles, then why should we doubt that mental states are identical to brain states? While the materialists theory isn't nearly as well evidenced as these other identity claims, it's still the best explanation of why mental states are so perfectly correlated to brain states. But surely the intuition that minds could persist in the absence of brains is no stronger than the intuition that water could exist in the absence of H2O, or that lightening could occur without a discharge of electrons.

But Kripke has an answer to this. He suggests our intuitions about the possibility of there being water without H2O are misguided. It's plausible, he thinks, that we are mistaking the one possibility with another: that there is something that is phenomenologically identical to water (that we have no way, short of a chemical analysis, to distinguish it from the stuff that fills our rivers and lakes and oceans) when there isn't any H2O. But, as Kripke argues, such an explanation misses its mark when applied to the materialists reductionist theory of mind. There cannot be anything that is phenomenologically identical to pain, and yet isn't pain. If someone thinks they're in pain, or is having an experience of being in pain, then they are in fact in pain. Pain, in other words, cannot be illusory. And so the materialist cannot use these other well established identity claims as partners in crime: the evidence incriminates him alone.

Kripke thinks he's successful in defending, at the very least, a presumption against materialism. But I think there's a further response the materialist can give. Granted, it's intuitive that unembodied minds could exist. But it's no less intuitive that the materialists theory could be correct, and that mental states could actually be identical to brain states after all. But of course, if mental states are identical to brain states then they are necessarily so, and premise (1) of Kripke's argument must be false. We thus have two equally valid but opposing intuitions. What do we do with them? I suggest they cancel each other out, and leave us without any presumption either for or against materialism.

But then we are back to where we started, with no reason to reject a materialist theory of mind and some fairly significant reason to accept it: along with ontological parsimony, the identity of mental states and brain states offers an attractive explanation of the appearance of supervenience. It seems, then, that if anything at the end of the day we are left with a strong presumption in favour of a materialistic reductionism of the mind.

Problems with Agent Causation

What is causation? As I understand it, if X causes Y then:

1. X and Y are temporally indexed propositions (or some metaphysical analog to propositions; i.e. facts)
2. X is temporally prior (or maybe simultaneous) to Y
3. X counter-factually entails Y

These three conditions seem to be built into our very concept of causation, and while maybe they are not alone sufficient, they surely seem necessary.

But this conflicts with the agent causation brand of libertarian freewill, which requires that causation is the sort of relationship that can involve—as operands—particular objects. Say the effect in question is "Sam's choosing to eat breakfast", then if it's a free choice it must be caused by Sam himself. It cannot be caused by any events containing Sam, or any sort of fact about Sam (e.g. his being hungry), but must be the object that is Sam. In this case, how can we understand causation? We must give up not only (1), but also (3) since particular objects cannot stand in counter-factual entailment relationships, and (2) since it makes no sense to talk about objects themselves being temporally indexed. Events containing objects might happen in some temporal order, and propositions about objects might be true at particular times, but it doesn't make much sense to attribute temporal attributes to persons. And even if it did, still Sam existed prior to the event, he exists while the event takes place, and hopefully he will continue to exist afterwards. So regardless, (2) must be given up.

In other words, to accept this brand of libertarian freewill, we have to reject everything we intuitively understand to be causation. Can the libertarian say; fine, maybe Sam's choosing to eat breakfast wasn't caused? Of course not: how could Sam exercise control in any meaningful way over an uncaused event? Such an event would be random, and randomness precludes freewill.

The libertarian might offer non-personal examples of 'object causation' in his defense, like a ball breaking a window. But to me this only sounds like a case of sloppy language. Everyone implicitly recognizes that when we say "the ball broke the window", what we really mean is "the ball hitting the window broke the window". Obviously if the ball had not hit the window, the window would not have broke. But then "the ball hitting the window" is an event, and not a particular thing: the cause and effect are both events. This therefore isn't actually a good example of object causation, because once we clarify what needs to be clarified, it's pretty obvious that it's really an event and not an object that's causing the window to break.

With all this said, it's very unclear how those who accept this brand of libertarian freedom can make sense of 'causation' without it ruining their view.

Conceivability of the GCB

Some argue that conceiving of something isn't as foolproof as we might typically think. This is a common response to Chalmer's philosophical zombie argument. When you're conceiving of a philosophical zombie, how do you know you're not really just thinking about a conscious person? What is different about the two conceptions? Is it that, in the one case, you're saying in your mind 'this thing is not conscious'? But surely being able to simply describe something doesn't amount to conceiving of it: even machines can do that. Indeed, we can even describe inconsistent scenarios, but it's odd to say such things can be conceived of.

It's like trying to conceive of a transparent block of iron. Close your eyes, can you do it? Once you've managed to conjure up an image, ask yourself; how do I know this isn't really just a block of glass?

Now turning to theological matters: how do you know you're thinking of the greatest conceivable being? Is it simply because you're saying in your head, "this thing is greater than anything else I could conceive"? Indeed, how do you know it's not the second or third greatest, rather than the first? It seems Anselm's God is like the transparent iron, or the philosophical zombie: even if such a thing is conceivable, we don't have good reason to believe it.

Divine Hiddenness and Hitchens Worlds

It is often argued that the absence of decisive reason to believe in God is, in of itself, reason to disbelieve. This is known as the problem of divine hiddenness and, much like the problem of evil, identifies features of the world that are unexpected under the assumption of classical theism. One might note that, if God were to exist, he would want to cultivate a personal relationship with all of his creation. But many people, despite being open to theistic belief, find themselves unable to shrug off rational doubts. Because it's impossible to have a relationship with someone you don't even believe exists, these rational doubts stand as a inculpable roadblock for people entering into this loving relationship with God. Divine hiddenness offers a very different sort of challenge than the problem of evil, and incites theists to develop novel theodicies to explain why God would permit rational disbelief.

Some have supposed that, even if God made his existence apparent to all, it would only result in greater numbers of people who would reject him. Knowing God existed, people would beg him to save them from evil. But God would not do away with those evils anymore than he does now, and this would plausibly make people bitter against him. People like the late Christopher Hitchens, not simply being atheist but being anti-theist, might become the norm. Instead of simply not believing in God, they would hate God and actively resist him. Such is a Hitchens world, one in which a large portion of creation hates their creator and actively resists a relationship with him all the while accepting his existence.

Supposedly God can work around non-belief. If one does away with any idea of a hellish afterlife for non-believers, they can reasonably think God doesn't simply give up on his creation at their death. Rather God would pursue his creation into eternity, so that eventually every person would have opportunity to love and be loved by him. But a Hitchens world would be dastardly for God's goal of bringing all of creation to himself. Plausibly, these powerful negative emotions towards God could do more damage and stand as a much bigger roadblock to a loving relationship with God than mere non-belief.

While this theodicy has an air of plausibility, there are a number of holes that would have to be filled before it could be called a success. First of all, it would be rather strange for God to give us decisive reason to believe his existence, but not his moral perfection. Indeed, on classical definitions of God, any decisive reason to believe his existence would necessitate decisive reason to believe his moral perfection. And so in a Hitchens world, everyone would be fully aware and in agreement that God is morally perfect, and that every evil he permits he does so for very good reason. But how could people then hate God? It would require them to be incredibly petty, or immature, or irrational.

God, being the creator of man, is supposedly directly responsible for human psychology. If we responded immaturely or irrationally to his justified permission of evil, then it could only be because he chose us to be that way. God could have just as easily created us to be more charitable and humble in our attitudes and judgements. It's not clear why God wouldn't simply have created us with different (and, in fact, more noble) psychological tendencies. In light of this, it's still very unexpected that he would hide his existence from creation.

Secondly, the real world is populated by a great many religious people who are wholly convinced of God's existence. And yet, hatred of God doesn't run rampant within theistic communities. In fact, if anything, it seems conviction in theistic belief has the complete opposite effect.

A Dilemma for Divine Command Theorists

I am expanding and hopefully improving on a previous argument against divine command theory, given here. According to divine command theory, the wrongness of an action is metaphysically identical to the actions being contrary to the commands of (a loving) God. My objection takes the form of a dilemma: Either God can issue commands to people knowing they will have rational doubts about its authenticity, or he cannot.

If he can, then we have a strong counter example to divine command theory. Surely having rational doubts about the authenticity of a command nullifies any obligation to obey it. For example, if you received a note from the government that lacked any official markings and appeared to be inauthentic, then you can't be expected to meet their demands. And if the government didn't even put any effort into presenting the command to you in such a way that you would recognize its authenticity, then it seems absurd to think you are under any obligation to do as they require of you. With this, it follows that it would be possible for God to issue commands without generating any obligation for the recipient to obey. And since facts about identity are non-contingent, divine command theory must be false.

If he cannot, then divine command theorists face a similar challenge that's almost as bad. For if God has issued someone a command, then as long as they are rational they will recognize that the command comes from God and not anyone else. But if a rational person is aware that God has issued them a command, then they are aware that God exists. And so, if a rational person has received a command from God (i.e. if they have a moral obligation), then they are aware that God exists. But there are many rational non-believers who do not believe and are not aware that God exists. And so there are an uncomfortably large number of people who must have never been issued any commands by God.

And so divine command theorists are impaled on either of the two horns of this dilemma: either they're confronted with a compelling counter-example to divine command theory, or they must admit there are a great many people for whom every action—no matter how monstrous—is morally permissible.

Divine Command Theory and the Obligations of Atheists

1. To issue a genuine command requires that you make an honest effort to make the recipient aware that you are the one commanding them (such that a rational person would recognize the authority and authenticity of this command).
    
2. God is omnipotent, and thus does everything he makes an honest effort to do.
    
3. Therefore, if God has issued someone a genuine command, then he must have made them aware the he is the one commanding them. [1&2]
    
4. But if a rational person is aware that God is commanding them, then they are aware that he exists.
    
5. Therefore, if a rational person is not aware that God exists, then they have not been issued any commands by God. [3&4]

And of course from (5) it follows that, on divine command theory, rational non-believers have no obligations and can do no wrong. But that's absurd: atheists have obligations just as much as anyone else, so there must be some flaw in the argument. Premise (2) and (4) seem indubitable, so it all comes down to rejecting (1) or rejecting divine command theory.

But premise (1) is very plausible. Imagine getting mailed a note from the government, written in pencil on loose leaf paper, without any official markings, and no name signed at the bottom saying, "you're summoned for jury duty, show up at the court house next Thursday morning". You would throw the paper away immediately, and it would seem rather silly to think you were the recipient of a genuine command, or that you had any obligation to obey. If the commander hasn't even tried to issue the command in such a way that a rational recipient would recognize its authenticity then, though the commanders will has been expressed, this expression doesn't seem to amount to a genuine command. But of course this is what scripture or religious tradition looks like to rational non-believers, and they will be very justified in doubting the authenticity of purportedly divine commands.

A Bayesian Response to External World Skepticism

The skeptical argument against the real world hypothesis (RWH) is this:

1. If I'm not justified in believing I'm not a brain in a vat, then I'm not justified in believing I have hands
2. I'm not justified in believing I'm not a brain in a vat
3. Therefore, I'm not justified in believing I have hands

Premise (1) follows from the undeniable closure of justification on known entailment. And so you might try objecting to premise (2) by saying you are in fact justified in rejecting the possibility of being a brain in a vat. You might say, look here I have hands! Here's one, and here's the other. I can feel them, I can touch them: is this not good enough reason to believe they are real? But, then again, if this all was an illusion and you were just a brain in a vat, what would you expect to be any different? Every experience of having hands just as well supports that you have hands, as it supports that you're a brain in a vat being tricked into thinking you have hands.

By the very construction of a skeptical hypothesis (SKH) it has the consequence that, for all possible experiences e, e is just as much expected on SKH as it is on RWH; Pr(e|SKH) = Pr(e|RWH). This is a plausibility rather than a probability judgement, in that the Pr function outputs the level of expectation or surprise we have (or should have) in the operands.

Baysians update their beliefs in accordance with Bayes theorem upon being presented with evidence. And so given that the two hypotheses are empirically equivalent, as long as the priors are also equal, it would be impossible for the Baysian to confirm RWH over SKH on evidential grounds. But now consider how the disparity between two hypotheses grows exponentially as evidence is accumulated, and how much evidence we really have (every experience of every moment of our lives). Even if two hypotheses are empirically equivalent, the same evidence could support one dramatically more than the other if the priors weren't equal. And, given that the two hypotheses are incompatible, we are then forced to reject SKH in favour of RWH. We can, then, happily say that we know SKH to be false. Notice that I am not simply Moore shifting. I am not saying I know SKH is false because I know RWH is true. In fact, even under the assumption that I don't have good enough reason to believe RWH, we still have good enough reason to reject SKH. The skeptical hypothesis is still defeated, even if the real world hypothesis cannot be established. And so, if we could justifiably say that Pr(RWH) is even a little bit greater than Pr(SKH), then we could have a solid answer to external world skepticism.

It all comes down, then, to establishing these priors. Traditionally Baysians address the priors of two competing hypotheses by simply ignoring them. They would say; set the priors to whatever you would like, and given the accumulation of enough evidence one hypothesis will eventually overwhelm the other. If we see a dramatic tendency for one hypothesis to be better evidenced than another, we can inductively infer that this pattern will continue and that future findings will continue to favour the one over the other.

But of course this strategy fails here, since the RWH and the SKH are empirically equivalent. You can gather as much evidence as you'd like, it will never favour one over the other as long as the priors are equal. The Baysian is then left with two options. On one hand he can arbitrarily set the prior probabilities to favour RWH, and in doing so give a rather unsatisfying answer to the skeptic. If all we can muster is an arbitrary rejection of skepticism, then it seems we have failed to offer a genuine response. On the other hand, the Baysian can seek out a priori principles to guide our judgement of priors. There is already one such principle at play, the principle of indifference: in the complete absence of probabilistic information, we should treat the priors as if they are equal. And it is exactly this, or at least something very much like it, that fortifies the skeptics argument.

Notice that this principle is cashed out in terms of what we should do, or what our expectations should be. But what sorts of principles could these be? It seems futile to come up with principles that track the objective probability of a hypothesis. So we should understand these principles as guiding our expectations. But then there is something inherently normative about these principles: they tell us about appropriate expectations to have. An epistemic realist (a term coined by analogy to moral realism) might say that there are simply normative facts governing how we should compare hypotheses. They might say that someone who accepts ad hoc explanations is doing something they simply shouldn't be doing. And it's not because ad hoc explanations are more likely to be false (indeed, it's unclear how such a claim might be defended), but simply that an explanations being ad hoc constitutes reason in of itself to reject it or, at least, be more suspicious of it.

Indeed there are probably many more intrinsically good or bad features for a hypothesis to have, like parsimony, explanitory fit, falsifiability, or even aesthetic appeal.

What we need are a priori principles by which we can favour one hypothesis over another. And this we have. It's naturally thought that parsimony and explanitory power are intrinsically good features for a hypothesis to have. And, being ad hoc or unnecessarily complicated are intrinsically bad features for a hypothesis to have.