He took up the problem yet again, four years later, in “The Only Possible Basis of Proof for a Demonstration of God’s Existence” (Einzig möglichen Beweisgrund zu einer Demonstration des Daseins Gottes), in order to present his view of teleology, in both the positive and negative senses, systematically and exhaustively, and to give it a foundation. Here he finds the proof for the existence of the divine being, customarily drawn from the purposive arrangement of the world, largely proportioned “alike to the worth as to the weakness of the human understanding.” But this latter point he raises more acutely than before, and points out the fundamental defect clinging to the whole methodology of physico-teleology. The conviction that flows from it may be “exceedingly sensory and hence very lively and gripping and both accessible and comprehensible to the most ordinary understanding,” but at no point can it stand up to the strict requirements of conceptual knowledge. For even supposing it were proved that order arose from disorder, a “cosmos” from “chaos,” by specific divine actions, that primordial being which ought to be thought as infinite and all-sufficient will precisely thereby labor under a basic limitation laid on it from outside. If crude matter is the opponent which this being has to overcome and it displays its goodness and wisdom only in that victory, then if the proof is not to lose all its meaning and effectiveness this matter has to be recognized as something in itself, as a given stuff with which the purposeful power must occupy itself. Hence this procedure can only serve “to prove an originator of the connections and artful composition of the world, but not of matter itself and the creation of the elements of the universe.” God will by this route always be shown only as master craftsman, not as creator of the world; the order and formation of matter appears as the work attributable to Him, but not its generation.
In this way the very idea of purposiveness of the world which is supposed to be establshed is put in extreme jeopardy. For there now enters into the world a basic dualism which, no matter how hard one may try to conceal it, is ultimately ineradicable. The shaping of the sheer stuff of being by intentional will is never absolute, but always something relative and conditioned: there is, in this mode of intuition, at least a definite substrate of being which as such does not carry the form of reason in itself but rather is opposed to it. The gap in the physico-theological proof is at this point clearly visible; it can be plugged only if we succeed in showing that what we have assumed to be the real and independent “essence” of matter and from which we can deduce its universal laws of motion is not alien to reason’s regulation but rather is an expression and a particular manifestation of these very rules.
Ernst Cassirer, Kant’s Life and Thought