Do not use power to suppress opinions you think pernicious, for if you do the opinions will suppress you.

The mind is a strange machine which can combine the materials offered to it in the most astonishing ways.

The rules of logic are to mathematics what those of structure are to architecture.

A habit of basing convictions upon evidence, and of giving to them only that degree or certainty which the evidence warrants, would, if it became general, cure most of the ills from which the world suffers.

The whole problem with the world is that fools and fanatics are always so certain of themselves, and wiser people so full of doubts.

The resistance to a new idea increases by the square of its importance.

Animal rights, taken to their logical conclusion, mean votes for oysters.