Anthony Flew and Paul Tillich have diametrically opposed views about the existence of God. Flew's brand of atheism has been characterized as a prime example of British positivistic naturalism, whereas Tillich's defense of theism can only be considered in the context of existential theology. The premises and structures of their arguments are so divergent that any discussion of them can at best be likened to a comparison of apples and oranges. That, however, will not deter us from attempting to explore the differences between Flew and Tillich, with special attention to the theological, logical, and symbolic aspects of their arguments.
Flew's argument is based on the premise that the universe is all that there is and that everything must therefore be explained by reference to the laws which seem to order it. Naturalism, by definition, has its foundation in empirical science; it presumes that the material world is understandable primarily through the experimental method. Flew expresses his own style of naturalism through the principle that he calls the "Stratoconian Presumption," named after the Greek philosopher Strato who first formulated it. Flew's version of the Stratoconian Presumption is as follows: "The presumption, defeasible by adverse argument, must be that all qualities observed in things are qualities belonging by natural right to those things themselves; and hence that whatever characteristics we think ourselves able to discern in the universe as a whole are the underivative characteristics of the universe itself" (Masterson, 1971, p. 118).
In other words, Flew contends that the universe is essentially just as it appears to be, and that the explanation for it is to be found within the natural realm rather than in the supernatural. He says that the laws of matter and energy seem perfectly capable of explaining those things that require explanation, and that the things that they do not explain do not require any ...