A religion is a unified system of beliefs and practices relative to sacred things, that is to say, things set apart and forbidden-beliefs and practices which unite into one single moral community called a Church, all those who adhere to them.

Sadness does not inhere in things; it does not reach us from the world and through mere contemplation of the world. It is a product of our own thought. We create it out of whole cloth.

Too cheerful a morality is a loose morality; it is appropriate only to decadent peoples and is found only among them.

The man whose whole activity is diverted to inner meditation becomes insensible to all his surroundings. His passions are mere appearances, being sterile. They are dissipated in futile imaginings, producing nothing external to themselves.

A monomaniac is a sick person whose mentality is perfectly healthy in all respects but one; he has a single flaw, clearly localized. At times, for example, he has an unreasonable and absurd desire to drink or steal or use abusive language; but all his other acts and all his other thoughts are strictly correct.

Even one well-made observation will be enough in many cases, just as one well-constructed experiment often suffices for the establishment of a law.

It is only by historical analysis that we can discover what makes up man, since it is only in the course of history that he is formed.