God has created the world, but he also sustains it in existence; without this sustenance, the world would disappear like a candle flame in a high wind. Further, God governs the world in such a way that it displays a certain constancy and regularity. These regularities are everywhere: heavier-than-air objects dropped near the surface of the earth fall down rather than up; bread is nourishing but mud is not; there is breathable air near the surface of the earth, though not at 35,000 feet or under water. Unlike rocks, seeds planted in soil sprout and take root; heavy steel beams will hold a lot of weight for a long time; a confined explosion will exert pressure on the wall of its container. It is by virtue of these regularities that human beings can act in the world, can learn about it, and act on what they have learned.
These regularities, of course, are what make science and technology possible. From the theistic point of view, the world God has designed and created is something like a vast machine, although that is perhaps too mechanical a term. (Perhaps it should also be thought of as something like a vast organism, or perhaps some amalgam of machine and organism.) In any event it is a structure of enormous complexity. (Think of the incredible complexity of a living cell, with its own hundreds of substructures in the form of molecular machines.) From a theistic point of view, one task of science is to come to know something about this wonderful structure — to learn about it in the systematic and communal way that is characteristic of science. Theism is thus, as such, not only hospitable to science, but enthusiastic about it. It is because God has created the world with these regularities and structures that it can be apprehended and known (to a significant degree) by creatures such as we are. It is because God has created us human beings in his image that we are able to apprehend and know the world.
A particularly interesting feature of the theistic view of the world, in this context, is that God created the various structures of the world freely. First, God wasn’t obliged, by his nature or by some antecedent structure, or by anything else, to create anything at all. And given that he does create, he wasn’t obliged to create just the things he did create. He has created horses, anacondas, and paramecia; he wasn’t obliged to create any of them. And given that he creates the things — horses, for example — that we do in fact find, he wasn’t obliged to create them with just the properties they do in fact have. It’s not a necessary truth that horses have the number of teeth they do have, or a stomach works just the way an equine stomach does work. Further, given that he has created the creatures the world displays, he wasn’t obliged to create them in any particular manner; he could have created them all specially, or, as presently seems more likely, by way of some evolutionary process. These things are all contingent; God could have done things differently. We ordinarily think that it is by reason that we know necessary truths; we know these things a priori, prior to or in some way independent of experience. Our knowledge of contingent truths, on the other hand, is (at least in part) by experience. Now the theistic idea is that what laws or regularities the world displays is a contingent matter; the same goes for the sorts of structures and organisms the world contains, and the properties of those structures and organisms. This suggests that science, as a systematic effort to come to knowledge of the world God has created, will have to be significantly empirical. From a theistic point of view, we can perhaps see this as the root of the empirical nature of science.
There are stories about early opponents of modern science refusing to count the number of a horse’s teeth or look through a telescope to see how many moons Jupiter has. These stories may or may not be true; nevertheless they illustrate a point. If you think you can figure out the number of teeth in a horse’s mouth a priori, you won’t feel obliged to open that horse’s mouth and actually count them. If you think you know just by reasoning that Jupiter has no moons, you won’t feel compelled to actually take a look through a telescope to see how many there are. (If the result of looking agrees with reason, the looking is unnecessary; if it doesn’t, it is misleading.) On the other hand, if you think the world and its structure are contingent — contingent on God’s freely choosing to make them one way as opposed to other possibilities — you’ll think looking to see is the appropriate way to find out. In this way the empirical nature of science, as well as its basic charter, arise out of a theistic way of looking at the world and fit in well with it.