A book that I rate only second in importance in evolution theory to Darwin 's Origin (this as joined with its supplement Of Man), and also rate as undoubtedly one of the greatest books of the twentieth century
Natural selection is not evolution.
It was Darwin's chief contribution, not only to Biology but to the whole of natural science, to have brought to light a process by which contingencies a priori improbable, are given, in the process of time, an increasing probability, until it is their non-occurrence rather than their occurrence which becomes highly improbable.