Sunday, May 1, 2011
Daily affirmation
Induction and the Axiom of Choice
Now as concerns the argument, its conclusion is that in induction (causal inference) experience does not produce the idea of an effect from an impression of its cause by means of the understanding or reason, but by the imagination, by “a certain association and relation of perceptions.” The center of the argument is a dilemma: If inductive conclusions were produced by the understanding, inductive reasoning would be based upon the premise that nature is uniform; “that instances of which we have had no experience, must resemble those of which we have had experience, and that the course of nature continues always uniformly the same.” (Hume THN, 89) And were this premise to be established by reasoning, that reasoning would be either deductive or probabilistic (i.e. causal). The principle can't be proved deductively, for whatever can be proved deductively is a necessary truth, and the principle is not necessary; its antecedent is consistent with the denial of its consequent. Nor can the principle be proved by causal reasoning, for it is presupposed by all such reasoning and any such proof would be a petitio principii.
For it amounts to nothing more than the claim that, given any collection of mutually disjoint nonempty sets, it is possible to assemble a new set — a transversal or choice set — containing exactly one element from each member of the given collection.
But might there be some feature of the proof that compromises its ability to offer the kind of justification we are after? One aspect of the proof that suggests itself is its reliance on the Axiom of Choice....
Where a condition on conceptual coherence is consistency with ZFC, Zermelo-Fraenkel set theory plus the Axiom of Choice, a theory most mathematicians believe to be true and indispensable for the formal development of mathematics.
If this is the justification then it would render the whole proof implausible because as Penelope Maddy has correctly pointed out, mathematicians have "accepted" the axiom of choice largely because of pragmatic reasons (for ease of proving some theorems like Zorn's lemma). They haven't accepted it because of its philosophically sound obviousness (in fact, many of them and logicians and philosophers have skeptically questioned its truth much as the later have inductive reasoning). Given these pragmatic historical considerations, they seem to mirror the pragmatic considerations of why people accept inductive reasoning as generally true (how will we live without assuming natural regularity and uniformity?).
Saturday, April 30, 2011
Animalism
Tuesday, April 26, 2011
The modal argument for dualism
Here's what I understand about this argument. Versions of it has been used by Kripke and Chalmers and here by Plantinga to argue that we are not our bodies or brains. The argument goes like this: Imagine yourself without a body. That seems easy enough. Can you imagine your body without its body? It seems not. That would be patently contradictory. Thus, your mind must have at least one property that your body doesn't: namely the modal property of possibly existing without a body. By Leibniz's law, they cannot be identical. That law simply says that everything has the property it has. If A has a property B does not have, they are not identical by that law. Your mind would have the modal property of possibly existing without a body while your body cannot exist without itself.
There are at least two ways to attack this. One may wish to deny Leibniz's law for modal properties; that is, one may wish to assert that it is possible for some things to have some modal properties they don't have. But I don't see this as a plausible avenue. It seems to me that Leibniz's law is true unrestricted, true for all properties, genuine, relational and modal.
So I will concentrate on the other possible objection which I will term the epistemic constraint to modality (ECM). It may seem plausible at first that anything one can imagine being true may be true in some possible world. Your car may be green when it is actually red. We know that your car has the modal property of possibly being green. How do we know that? We just imagine it so and if we can imagine it so, it is possible it is so. That's how we seem to know what is and isn't possible in the broadest sense. I can imagine your car being green when it's red and thus it must have the modal property of possibly green. I cannot imagine your car being green all over and red all over at the same time and thus your car must not have the modal property of being possibly green and red all over at the same time.
But does this kind of epistemic access always cut modality at its joints? Cut it precisely such that the space of epistemic possibility covers the same space as the modal space? Let's imagine we live 500 years ago. We would know what water was. It's that clear, potable, odorless liquid. Can we imagine it not being H2O? Yep, I believe we can. We could imagine it being XYZ for example. But we now know that water = H2O. It could not have been possible that water did not turn out to be H2O because water = H2O is a necessary identity statement. This is a case where our epistemic space over steps the boundaries of possibility. Thus zombies may not be possible though we can (now) imagine them.
Defenders of the claim that epistemic space and modal space are perfectly overlapping can deny that people 500 years ago really can imagine that water = H2O because they are not thinking about water when they imagine it not being H2O. But this doesn't seem like a way to defend that claim because then how would we know we are talking about or believing anything about some putative object when we imagine it being so (having some property) when science may tell us one day that it does not have that property? It doesn't seem that my ability to refer and to think about things are so dependent on contingencies in future scientific discovery.