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.

A person is not merely a single subject distinguished from all the others. It is especially a being to which is attributed a relative autonomy in relation to the environment with which it is most immediately in contact.

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.

Social life comes from a double source, the likeness of consciences and the division of social labour.

The man whose whole activity is diverted to inner meditation becomes insensible to all his surroundings.

To pursue a goal which is by definition unattainable is to condemn oneself to a state of perpetual unhappiness.

Man could not live if he were entirely impervious to sadness. Many sorrows can be endured only by being embraced, and the pleasure taken in them naturally has a somewhat melancholy character.