Free Where the Conflict Really Lies: Science, Religion, and Naturalism by Alvin Plantinga

processes that give rise to it? Perhaps it
is
irrational to do that, but surely some argument is needed; one can’t simply assume that it is. Why treat the sources of religious belief differently? Is there anythingbut arbitrariness in insisting that any alleged source of truth must justify itself at the bar of rational intuition, perception, and memory? Perhaps we have several
different
sources of knowledge about the world, and none can be shown to be reliable using only the others. Once more, arbitrarily lowering the net (or missing the ball).
    By way of summary: Quentin Smith, himself a naturalist, deplores the “desecularization” of philosophy over the past quarter century or so. He complains that most naturalist philosophers ordinarily know nothing about contemporary philosophy of religion and pay little heed to it, “but the great majority of naturalist philosophers react by publicly ignoring the increasing desecularizing of philosophy (while privately disparaging theism, without really knowing anything about contemporary analytic philosophy of religion) and proceeding to work in their own area of specialization as if theism, the view of approximately one-quarter or one-third of their field, did not exist.” 29 Dennett only partially fits this pattern. True, he doesn’t know anything about contemporary analytic philosophy of religion, but that doesn’t stop him from making public declarations on the subject. 30
II DRAPER’S ARGUMENT
     
    I’ve argued so far that evolution and theism, contra Dawkins and Dennett, are compatible: this means, as I am using the term, that there are no obvious truths such that their conjunction with evolution and theism is inconsistent in the broadly logical sense. One might argue, however, that even if this is so, the truth of evolution gives us some reason to reject theism: perhaps evolution constitutes
evidence
against theism. Paul Draper makes just this claim: “I will show thatcertain known facts support the hypothesis of naturalism over the hypothesis of theism because we have considerably more reason to expect them to obtain on the assumption that naturalism is true than on the assumption that theism is true.” 31 What are these “known facts”? One of them, he says, is evolution: “My position is that evolution is evidence favoring naturalism over theism. There is, in other words, a good
evidential
argument favoring naturalism over theism.” 32 The basic idea is that evolution is more likely—at least twice as likely, Draper argues—on naturalism than on theism.
    His argument goes as follows. Where “E” is evolution (that is, the proposition that all current forms of terrestrial life have come to be by way of evolution), “T” is theism, and “N” is naturalism, Draper proposes to argue that
(1) P(E/N) is much greater than P(E/T).
     
    From this he infers that if all else is (evidentially) equal, naturalism is more likely than theism. Given that naturalism is incompatible with theism, it follows that theism is unlikely.
    Suppose, however, as most theists who have thought about it do think, that theism is noncontingent: necessarily true or necessarily false. If so, (1) doesn’t imply that naturalism is more likely than theism; instead (1) obviously entails that theism is true. For if theism is noncontingent and false, then it is necessarily false; the probability of a contingent proposition on a necessary falsehood is 1; hence P(E/T) is 1. But if, as Draper claims, P(E/N) is greater than P(E/T), then P(E/T) is less than 1, hence T is not necessarily false. If T is not necessarily false, however, then (given that it is noncontingent) it is necessarily true. So if theism is noncontingent, and (1) is true, then theism is true, and indeed necessarily true. Draper is of course assuming that theism is contingent; hence his argumentwon’t be relevant if theism is noncontingent. But let’s set this limitation aside and look at his interesting argument.
    How does the