I never guess. It is a capital mistake to theorize before one has data. Insensibly one begins to twist facts to suit theories, instead of theories to suit facts.

Every mental state is a function of some physical state of the brain.

The natural price of labor is that price which is necessary to enable the laborers, one with another, to subsist and to perpetuate their race, without either increase or diminution.

对感受者而言，生活是悲剧；对思考者而言，生活是喜剧。

The only way to predict the future is to have power to shape it.