The enterprise of Christian apologetics incorporates a broad range of intellectual disciplines, such as history, philosophy, theology, physics, ethics, mathematics, fine arts, biology, and literature. It’s a beautiful and remarkable thing that virtually every avenue of mankind’s scholarly exploration has yielded significant support for Christianity. The result is a spectacular mosaic that, unless Christianity is actually true, should never have materialized, much less in such high definition. The picture that has emerged over the past two thousand years, the product of man’s attempt at a comprehensive study of reality, is an argument itself, I think.
Notice, however, that when some of these relevant disciplines are taken individually, the evidence they provide doesn’t get you all the way to Christian theism. It may get you to a rather vague theism, or even a theism with strong Christian flavor, but no further. We don’t see the creeds spelled out in nature. We should be mindful of this so as not to overstate a claim and in order to hold the non-theist accountable when (not if) they try to argue against the existence of God in general by criticizing Christian theism in particular. We must not underestimate the value of these disciplines; they are crucial for the foundation upon which our broader project depends. They constitute what some have called our pre-apologetic.
A subset of these disciplines make up what is referred to as natural theology, which is, for me, an area of keen academic interest. Natural theology explores the questions of the existence and nature of God without examining Scripture or other forms of alleged divine revelation. Instead, the practitioner philosophically reflects upon observations of the natural world and draws metaphysical conclusions–i.e., that God exists and has certain attributes. This stands in contrast to revealed theology, which is wholly dependent upon special revelation (Scripture, for example). Historically, natural theology has been employed by some adherents of all the major monotheistic religions–Christianity, Judaism, and Islam–as well as some prominent thinkers who rejected all of those characterizations of God (think Voltaire and Spinoza).
You’re probably familiar with at least a few of the arguments developed by natural theology, even if you haven’t heard them labeled as such. The Kalam cosmological argument for the existence of God, which incorporates logic and astrophysics, is the poster child. The fine-tuning argument and the argument from consciousness are other better-known examples. While science often factors in, it doesn’t always. For instance, natural theology also includes the moral argument and the argument from the existence of evil.
There is much debate over whether intelligent design arguments based on biological observations qualify as natural theology. Dr. William Dembski, a key figure in the contemporary intelligent design (ID) movement, says that they do not. Specifically, he says that the ID program is not a theological endeavor, although he notes that its conclusions have implications for theology. I agree with Dembski on this careful delineation. There are indeed supporters of ID research who are not theists and some who see ID as evidential support for fringe-science hypotheses, such as life having been engineered and seeded on earth by a distant alien civilization (directed panspermia).
But, I am convinced that we can and should use the positive arguments for design from biology in the practice of natural theology. By “positive arguments” I mean the characteristics of life that indicate, often by analogy, the activity of a Designer. To be clear, such arguments do not rule out evolutionary common descent, they only point to things like planning, guidance, and purpose in biology. Materialists are highly critical of this approach, saying that the appearance of design in living things is illusory, the product of blind, purposeless processes. This actually boils down to philosophical pre-commitments, because science, as such, cannot prove or disprove a metaphysical claim. However, I believe the case for God based upon natural theology is much stronger than the case for the absence of God based on natural observations, hence the value of this approach.
Ultimately, our dialogue with non-theists must begin with the logical first thing, which is the existence of God. If someone has dismissed the validity of Scripture wholesale, we can’t use special revelation as the starting point. Our common ground, then, must be the observation of the world around us. I see natural theology as a powerful first stepping stone in the cumulative case for Christianity. I also believe that Scripture endorses it. Romans 1:20 says, “For His invisible attributes, that is, His eternal power and divine nature, have been clearly seen since the creation of the world, being understood through what He has made. As a result, people are without excuse.” And Psalm 19:1 says, “The heavens declare the glory of God, and the sky proclaims the work of His hands.”
For further reading, I recommend The Blackwell Companion to Natural Theology edited by Dr. William Lane Craig and Dr. J.P. Moreland and In Defense of Natural Theology: A Post-Humean Assessment edited by Dr. James F. Sennett and Dr. Douglas Groothuis.