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Wednesday, January 14, 2009


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I agree with you here, and also suspect that explanatory rationalism ceases to be appealing when applied to practice. It seems to me that what explanatory rationalism would do in many a situation is lead to the philosopher's nightmare - the infinite regress.

If P is explained by Q (a seperate and distinct set of facts from P), then to be consistent as an explanatory rationalist, would you not have to hold that Q is explainable by R and R by S and S by T, etc, etc, etc,? If so, then there is no stopping. If not, then at some point, there must be a set of facts not itself explainable by appeal to some other set of facts.

In practice, one of the best examples of this are theological questions like: "Why is the world this way rather than that?" Any answer - "Because God is this way rather than that," for instance - provokes another "why" question and if one wants to, one can simply keep asking "why" to every answer ad infinitum.

We can say that P is true because each conjunct of P is true. We are not forced to say that P is true because of a proposition Q which is a conjunct of P.

The worry is supposed to be that have not provided a contrastive explanation. We know that the conjunction is true iff. all of it's conjuncts are true. But the dialectical pressure comes from the question why conjunction P rather than P+? That is, why this particular maximally consistent contingent conjunct (we might as well say, 'why this world?') and not another possible world? We have conceded that the world we inhabit is contingently actual. That concedes that another world might have been actual. That raises the question of why some other world isn't. Why this one rather than that one? There is a subtle shift in the kind of explanation sought, though, since now we are looking for an explanation in terms of final causes. Leibniz offers the final cause that this world is actual because God aims at the best, and this is the best world. But I guess other final causes are available. The upshot is that, if we cannot offer a contrastive explanation (if there is no reason why this world is actual rather than some other), then all we can offer is the brute fact that it just so happens that this is the actual world or that's how chance would have it.

Hello bill,

Your argument is that it's adequate to explain the truth of the conjunction A&B by offering the separate truths A and B. I'm not so sure. P is supposed to be a conjunction of contingent truths. But from A, B there follows A&B necessarily. Offering A and B does nothing to explain the contingency of A&B. For this we need an explanation of the contingency of A and B individually, something more than their mere truth.

Hi David,

Let C = A & B. If one or both of the conjuncts are contingent, then C is contingent. Suppose we ask: Why is C true? My claim is that we can explain why C is true by simply saying that each of its conjuncts is true. We can say the same with respect to P: it is true because each of its conjuncts is true. (I don't see that it matters whether we take P to be the conjunction of all contingent truths, or whether we take P to be the conjunction of all truths both contingent and necessary. Either way, P will be contingent. Note also that if P were necessary, the question why it is true would lapse. What cannot be otherwise has its explanation in itself.)

You say, "But from A, B there follows A&B necessarily." That's right, but of course it doesn't imply that A&B is necessarily true. The necessity of the consequence is not the same as the necessity of the consequent. Same goes for P: given every truth, their conjunction P follows.

You say, "Offering A and B does nothing to explain the contingency of A&B. For this we need an explanation of the contingency of A and B individually, something more than their mere truth." I'm not getting your point. If the question is: why is A&B contingent, I say it is because its conjuncts are contingent. If you ask why A (or B) is contingent, I say that A records a fact that might have been otherwise.

Hi Bill,
Looking at my comment again I can see I haven't been very clear. For me, an explanation of the truth of A&B must involve an explanation of the truth of A and an explanation of the truth of B. It hardly seems adequate to say that A&B is true because A and B are true. Why is it true that am I short and fat? Well, because I am short and because I am fat! Hardly very explanatory, surely? If asked to prove the proposition A&B one would have to prove A and B separately, I think. I agree that "Someone who understands why A is there, why B is there, and why C is there, does not need to understand some further fact in order to understand why the three of them are there." But then you move to "Similarly, it suffices to explain the truth of a conjunction to adduce the truth of its conjuncts." If 'adduce' means 'explain' then I agree, but I think you are using 'adduce' to mean 'state'.

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