The Fifth Way, also remixed

Thomas writes:

We see that things which lack intelligence, such as natural bodies, act for an end, and this is evident from their acting always, or nearly always, in the same way, so as to obtain the best result. Hence it is plain that not fortuitously, but designedly, do they achieve their end. Now whatever lacks intelligence cannot move towards an end, unless it be directed by some being endowed with knowledge and intelligence; as the arrow is shot to its mark by the archer. Therefore some intelligent being exists by whom all natural things are directed to their end; and this being we call God.

Central to Aristotle’s thought is the normative thesis that all substances have proper functions or ends defined by their immanent forms. Moreover, Aristotle makes the statistical claim that for the most part things things function correctly—they function to fulfill their ends.

The statistical claim is epistemologically important: that an activity or structure is usually exhibited by members of a kind is a central piece of evidence for that activity’s or structure’s correctness. But logically the statistical facts and the normative facts are independent: it is logically possible for all sheep to be three-legged, or for only a few pecan trees to produce pollen.

To see that we are committed to the connection between the normative and the statistical facts, consider the ridiculousness of the hypothesis that one of the ends of salmon is to prove theorems about high-dimensional topology. The utter unsuitability of the salmon brain to that end is conclusive evidence against the hypothesis. But this is only if we think there is a connection between the normative and the statistical facts—without such a connection, we could simply suppose that all salmon fall short of their topological researcher nature.

Note, too, just how massive the coincidence between the normative and statistical facts is: we see it across millions of species.

As Aquinas concedes, in intelligent substances we have some hope of an explanation of the coincidence: the intelligent substance consciously aims at its self-fulfillment. (Though leaning on this may be too much of a concession, because we still need to explain why this aiming isn’t futile, like a crank’s attempts to trisect angles.) But why do unintelligent substances’ activities in fact harmonize with their self-fulfillment, and do so massively, across all the millions of species we have? Why is it that we do not salmon-like fish with mathematical activity as their purpose, snake-like reptiles with flying as their end, and apes whose primary purpose is turning their bodies into gold by exposure to solar radiation?

A theistic explanation of the massive coincidence is compelling, and it provides another theistic solution to the shortcomings of a pure Aristotelian system.