Just as the senses require sensible objects to stimulate them, so our powers of observation, recollection, and imagination do not work spontaneously, but are set in motion by the demands set up by current social occupations.

Where there is giving there must be taking.

Knowledge is no longer an immobile solid; it has been liquefied. it is actively moving in all the currents of society itself

Adequate control means that the successive acts are brought into a continuous order; each act not only meets its immediate stimulus but helps the acts which follow.

The origin of thinking is some perplexity, confusion or doubt.

Man is merely a frequent effect, a monstrosity is a rare one, but both are equally natural, equally inevitable, equally part of the universal and general order. And what is strange about that? All creatures are involved in the life of all others, consequently every species... all nature is in a perpetual state of flux. Every animal is more or less a human being, every mineral more or less a plant, every plant more or less an animal... There is nothing clearly defined in nature.

One might as well say he has sold when no one has bought as to say he has taught when no one has learned.