A federal court has decreed that teaching intelligent design is unconstitutional because it covertly inculcates belief in a divine being who is the cause of everything. This kind of judicial incompetence is the consequence in part of the likelihood that the judges do not know the difference between philosophy and theology, the first pursued on the basis of natural reason alone, the second the willing assent of faith. Intelligent design claims no more than St. Paul, in Romans 1:19-20, doing philosophy not theology, did in arguing that from the worlds we see we can infer the existence of the invisible things of God. This is not a theological argument; it does not rest on revelation, and no faith is required to see its reasonableness. It is the kind of argument, to use Aristotle’s words, that saves the appearances. It is what St. Thomas called a quia, or because argument, an argument that because certain visible effects exist, there must be a cause. Darwinian evolution is an account of this kind. From the existence of many extinct animals, from the aesthetic insight that many animals are of the same type, from the obvious fact that some species compete better than others, from the fact that mutations—another word for changes—occur, we infer the reasonableness of evolution.

Both Darwin’s theory and St. Paul’s are strong and weak. St. Paul’s theory is strong in that it seems to play to a kind of connatural conviction that the world is beautifully and reasonably ordered, and if ordered, ordered by some intellect. On the other hand, St. Paul’s conclusion is tested daily by the existence of evil and disorder. The gulag, the holocaust, cancer, and the beheading of innocents are realities. Darwin’s theory seems strong because it relates a vast body of evidence, skeletons, bone fragments, geological strata in an impressively intelligible manner. Darwin’s theory seems weak because the evidence, although impressive, is thin, and the imaginative construct on which it rests is simplistic. If the millions and millions of years of uniform change can be imagined as a tennis net a thousand miles long, the discrete evidence for which the net provides a relational field might be thought of as one thousand buckshot dispersed unevenly over its length. And why should the idea that simple things get bigger and more complex be considered self-evident?

Darwin’s theory and St. Paul’s are cousins under the skin. Both theories lack the notes of a genuinely scientific theory, such as, say, Newton’s laws or s = (1/2)gt2. Neither can be repeated, neither can be expressed mathematically, both exist in the controversial atmosphere caused by the presence of countervailing theories for which there is also some evidence. Though neither is theological, each is urged with a conviction that belongs to faith because the stakes are high. If Darwin is right, we may be children not of an intelligent designer but of the serpent. If intelligent design is right, we may have life-changing duties to the designer. The fact is that on a purely philosophic basis, we have no perfect theory of the origin of the world or man, just two contending, reasonable hypotheses.

Why are both theories reasonable, worthy of respect and consideration? Because they rest upon evidence and assume the existence of a philosophic principle called the principle of sufficient reason. This principle is no more complicated than the insight that makes us look for a thief rather than a malevolent fairy when our car disappears from the mall parking lot. For a judge to assume that this principle is presupposed quite correctly by every day-to-day activity, every scientific endeavor, by Darwinian evolution, by every theory but one, the dangerous theory called intelligent design, is an act partly of ignorance, partly of prejudice. And if it be said that the God whose existence St. Paul argued cannot be seen but is known only by his effects, let it be noted that the same is true of evolution: we see effects, we give their cause a name. Mr. Evolution is no more visible than the God whose existence St. Paul attested; both are invisible realities known and named from the visible things of this world.