On Evidence and Irrationality

One often hears the claim that Christians are, since they do not apportion their belief to the evidence, irrational. This must be carefully distinguished from the claim that Christianity is false. Though the claim that it is false might well entail that belief in it is irrational, they are yet distinct claims. The first is epistemological in kind, the second metaphysical.

I wish now to consider the epistemological claim - that claim that, since Christians do not apportion their belief to the evidence, they are irrational.

"Consider" is perhaps not the best word. "Attack" is better. Now, one might attack the epistemological claim is various ways. One might do so as did Thomas. He would attack my means of arguments meant to establish this or that Christian truth. (For my own part, I'm suspicious that arguments such as this can be made to work against the religious skeptic.) However I won't take the Thomas path. Instead I'll take on the charge of irrationality by means of a tu quoque. (Tu quoque is a form of rebuttal in which one claims that one's opponent violates some principle that he has put forward. This leaves one's opponent with two choices: (i) take back the principle, or (ii) take back the claim or claims he's made that violates that principle.)

Call the one who wishes to defend the claim of Christian irrationality in the way I've describe "Clifford". (William Clifford famously made the charge that Christians believe where there is no evidence and are thus irrational.) I think it clear that Clifford means to endorse some such principle as this:

One ought in all cases to apportion one's belief to the evidence available.

Call this putative principle "P". Now let us ask what seems an obvious question: What is the evidence available for P? I would guess that there is none on offer. (William Clifford certainly gives us none. Nor do any of the others of whom I know give us any reason to believe it.) Indeed it is difficult to think of what might count as evidence in favor of P. Let me explain.

Evidence for the truth of some claim is a set of propositions (perhaps a unit-set) the members of which are (i) all true, and (ii) together tend to show that the claim is more likely than not. (This isn't a complete definition, but it does state two necessary conditions; and those two are all we'll need.) Now, what might a set of propositions be that would tend to show P more likely than not? They would have to be epistemological, for P is epistemological; and they would have to be, in some sense, more basic or fundamental than P. (From the more basic or fundamental we derive the less basic or fundamental.) But if P were to be true, there would be no more basic epistemological principle from which it could be derived. It is the sort of principle that, if true, is absolutely basic. There is nothing "beneath" it which has the potential to prove it true. (Or so it seems to me upon reflection. My only argument here is this: I've looked and haven't found anytying more basic than it from which it might be derived.)

So, then, here's where we're at: very likely P has no evidential support. But if this is so, P is, if true, not to be believed. For if P is true, nothing - and this includes P - is to be believed without evidence. Where does this leave us? P ought not to be believed. For P is either true, or it is false. If true, then as we've seen it's not to be believed; and if false, then (as should be obvious) it's not to be believed. Conclusion: belief in P is irrational.

This is our tu quoque. Very likely the principle brought to bear upon Christianity - the principle P - can't pass the test that it itself sets up. The upshot of all this should be clear: we must all believe something without evidence if we're to believe anything at all. (This was also argued for here in a direct way. The argument of this post is indirect and proceeds by way of refutation of the contrary opinion.) We must, as it were, all strike out into the evidential void. Does this mean we're all irrational? It does not, for as we've seen the claim that lack of evidence entails irrationality is simply not to be believed. There is of course a lacuna here. We still need it explained to us how we can rationally believe a thing when we have no evidence of its truth. But I will not attempt to fill the lacuna here. Nor will I attempt to divide propositions into those that are in need of evidential support and those that are not. These tasks must be left for another day.

We must all strike out into the evidential void and plant a flag. I've planted mine. Clifford has planted his, but refuses to admit that he's done so. He says that the evidence must dictate where one plants it, but this very claim lacks evidence. If the Christian plants his flag arbitrarily, so does Clifford.