Just as iron rusts from disuse, and stagnant water putrefies, or when cold turns to ice, so our intellect wastes unless it is kept in use.

Darkness is absence of light. Shadow is diminution of light.

Although nature commences with reason and ends in experience it is necessary for us to do the opposite, that is to commence with experience and from this to proceed to investigate the reason.

Small rooms or dwellings set the mind in the right path, large ones cause it to go astray.

Oh! Speculators on things, boast not of knowing the things that nature ordinarily brings about; but rejoice if you know the end of those things which you yourself device.

The eye which turns from a white object in the light of the sun and goes into a less fully lighted place will see everything as dark.

Those who, in debate, appeal to their qualifications, argue from memory, not from understanding.