Rational and a priori theology stands or falls with the ontological argument; and if that argument—or some substitute for it, alleged to express its intent—still seems self-evidently cogent to a philosopher here and there, its fallaciousness is self-evident to all the rest. Natural theology, on the other hand, sets out from facts and inductions; its premisses are as firmly established and as universally acknowledged as any of the stable generalisations of science. Here there is at least common ground, as distinct from private certitude, from which argumentation may proceed. Coercive demonstration being confessedly unattainable, it is to be inquired what kind of justification for reasonable belief natural theology can afford. And the first step is to set forth the facts and generalisations which collectively constitute our data or premisses.
The forcibleness of Nature's suggestion that she is the outcome of intelligent design lies not in particular cases of adaptedness in the world, nor even in the multiplicity of them. It is conceivable that every such instance may individually admit of explanation in terms of proximate causes or, in the first instance, of explanation other than in terms of cosmic or 'external' teleology. And if it also admits of teleological interpretation, that fact will not of itself constitute a rigorous certification of external design. The forcibleness of the world's appeal consists rather in the conspiration of innumerable causes to produce, by their united and reciprocal action, and to maintain, a general order of Nature. Narrower kinds of teleological argument, based on surveys of restricted spheres of fact, are much more precarious than that for which the name of 'the wider teleology' may be appropriated in that the comprehensive design-argument is the outcome of synopsis or conspection of the knowable world.
(F. R. Tennant, Philosophical Theology, vol. 2, The World, the Soul, and God [Cambridge: Cambridge University Press, 1930], 79)
