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.

We have usually no knowledge that any one factor will exert its effects independently of all others that can be varied, or that its effects are particularly simply related to variations in these other factors.

The more highly adapted an organism becomes, the less adaptable it is to any new change.

Natural selection is not evolution.

The best causes tend to attract to their support the worst arguments, which seems to be equally true in the intellectual and in the moral sense.

The analysis of variance is not a mathematical theorem, but rather a convenient method of arranging the arithmetic.

The tendency of modern scientific teaching is to neglect the great books, to lay far too much stress upon relatively unimportant modern work, and to present masses of detail of doubtful truth and questionable weight in such a way as to obscure principles.