The emphasis in early Christian writings was not on complexity, irreducible or otherwise, but on the beauty, order, lawfulness, and harmony found in the world that God had made. As science advances, it brings this beautiful order ever more clearly into view. Every photograph from the Hubble Space Telescope, every picture from the ocean’s depths, every discovery in subatomic physics, shows it forth. As Calvin wrote in his Institutes of the Christian Religion, “God [has] manifested himself in the formation of every part of the world, and daily presents himself to public view, in such manner, that they cannot open their eyes without being constrained to behold him.” And, “[W]ithersoever you turn your eyes, there is not an atom of the world in which you cannot behold some brilliant sparks at least of his glory… . You cannot at one view take a survey of this most ample and beautiful machine [the universe] in all its vast extent, without being completely overwhelmed with its infinite splendor” [emphasis mine]. Note that “atoms of the world” are not irreducibly complex, nor is “every part of the world.” Irreducible complexity has never been the central principle of traditional natural theology.
But whereas the advance of science continually strengthens the broader and more traditional version of the design argument, the ID movement’s version is hostage to every advance in biological science. Science must fail for ID to succeed. In the famous “explanatory filter” of William A. Dembski, one finds “design” by eliminating “law” and “chance” as explanations. This, in effect, makes it a zero-sum game between God and nature. What nature does and science can explain is crossed off the list, and what remains is the evidence for God. This conception of design plays right into the hands of atheists, whose caricature of religion has always been that it is a substitute for the scientific understanding of nature.
Stephen M. Barr, “The End of Intelligent Design?”