When we consider a human work, we believe we know where the "intelligence" which fashioned it comes from; but when a living being is concerned, no one knows or ever knew, neither Darwin nor Epicurus, neither Leibniz nor Aristotle, neither Einstein nor Parmenides. An act of faith is necessary to make us adopt one hypothesis rather than another. Science, which does not accept any credo, or in any case should not, acknowledges its ignorance, its inability to solve this problem which, we are certain, exists and has reality.

Evolution of living organisms: evidence for a new theory of transformation (1977)