J.L. Mackie

“The argument from design, therefore, can be sustained only with the help of a supposedly a priori double-barrelled principle, that mental order (at least in a god) is self-explanatory, but that all material order not only is not self-explanatory, but is positively improbable and in need of further explanation...this double-barrelled principle is recognizable as the core of the cosmological argument...The argument will not take us even as far as Kant seems to allow without borrowing the a priori thesis that there is a vicious metaphysical contingency in all natural things, and, in contrast with this, the 'transcendental' concept of a god who is self-explanatory and necessarily existent. It is only with the help of these borrowings that the design argument can introduce the required asymmetry, that any natural explanation uses data which call for further explanation, but that the theistic explanation terminates the regress. Without this asymmetry, the design argument cannot show that there is any need to go beyond the sort of hypothesis that Hume foreshadowed and that Wallace and Darwin supplied... The dependence of the argument for design on the ideas that are the core of the cosmological one is greater than Kant realized.”