Experimental observations are only experience carefully planned in advance, and designed to form a secure basis of new knowledge.

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.

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 statistician cannot excuse himself from the duty of getting his head clear on the principles of scientific inference, but equally no other thinking man can avoid a like obligation.