The challenge for any mechanistic theory, then, is to explain the teleology of the human world in non-teleological terms.
Darwin himself spent a large part of the later years of his life in thus extending the new teleology.
The modern theory of evolution, on the other hand, has reintroduced a scientific teleology of another type.
But with the decline of dogmatic belief and the spread of religious doubt - as the special sciences also grow more general, and the natural sciences become more speculative about matter and force, evolution and teleology - men begin to wonder again about the nature and origin of things, just as it was the decay of polytheism in Greek religion and his own discoveries in natural science which impelled Aristotle to metaphysical questions.
The final conception of the Kantian philosophy is, therefore, that of ethical teleology.