Peter van Inwagen argued: "science is an outgrowth of western Latin Christianity, connected with it in much the same way as Gothic architecture". His claim is plausible historically. The non-Christian theistic scientist can claim that the aspects of Christianity that led to science are also found in her religion—say, the belief that the world is created by a God who would be unlikely to give us a thirst for knowledge that we could not possibly have satisfied. But the historical fact should give pause to the non-theistic scientist. She should ask herself whether the dependence of science on theism was merely historical or whether there is not an deeper dependence as well.
Consider this. Assuming one has good reason to be a theist, one has good reason to believe that simpler theories are more likely to be true and (perhaps equivalently) that induction is a good way of getting at truth. Moreover, connections like this between theism and scientific practice were in fact important to scientists like Leibniz and Newton. Now, the contemporary non-theist (except maybe an optimalist like John Leslie—but whether he counts a non-theist is unclear) does not in fact have anything to put in the place of theism that would give good reason to believe that simplicity and induction are good guides to truth. It would seem, thus, that one has to say one of two things: Either (1) the theistic underpinning of science did no real epistemic work in bolstering science in the first place, or (2) the non-theistic scientist's hope in science should be significantly lower than that of the theistic scientist.
Can one uphold (1)? I doubt it. It seems very plausible that there is something right about the idea that theism gives one a significant reason to have a hope in science as a guide to truth. But if so, then it is true that the non-theistic scientist has less reason for such hope.
Does the non-theistic scientist have any reason for such hope? That is a further question.