This is motivated by a conversation I had last month with a biology graduate student who felt intellectually superior to those in all disciplines outside of the natural sciences because they “rely on philosophy and not science.” Natural science assumes: (1) the existence of a external world that is independent of our theories about it, (2) the orderly structure and nature of that external world, (3) the existence of truth, (4) the knowability of that truth, and about the external world in particular, (5) the existence, not to mention the validity and reliability, of the laws of logic, (6) the reliability of our cognitive and sensory faculties to serve as truth gatherers and as a source of justified beliefs in our environment, (7) the adequacy of language to describe the world, (8) the existence of values used in science — for example, “test theories fairly and report test results honestly,” (9) the uniformity of nature and, thus, the validity of induction, (10) the existence of numbers and mathematical truths, and (11) that it is better to know and believe what is true rather than what is false. I am not saying these assumptions are false; I’m just pointing out that these are assumptions of natural science that cannot be verified by its own standards of knowledge. In other words, natural science has a philosophy about reality (metaphysics), knowledge (epistemology), and the good (ethics) whether it acknowledges it or not. And the conclusions of science cannot be any more certain than the presuppositions it rests upon, some of which cannot be rationally justified outside of a theistic worldview. The final barometer of rationality is in philosophy, not science.