History warns us that it is the customary fate of new truths to begin as heresies and to end as superstitions.

I believe that history might be, and ought to be, taught in a new fashion so as to make the meaning of it as a process of evolution intelligible to the young.

The results of political changes are hardly ever those which their friends hope or their foes fear.

The scientific imagination always restrains itself within the limits of probability.

Every great advance in natural knowledge has involved the absolute rejection of authority.