Not to engage in this pursuit of ideas is to live like ants instead of like men.

Habits are formed by the repetition of particular acts. They are strengthened by an increase in the number of repeated acts. Habits are also weakened or broken, and contrary habits are formed by the repetition of contrary acts.

If one wants another only for some self-satisfaction, usually in the form of sensual pleasure, that wrong desire takes the form of lust rather than love.

Emancipation of human labor from economic servitude and exploitation, i.e., from organizations of production in which the conditions of work are determined by a master class who own the means of production, and in which the fruits of work are alienated from workers to the benefit of masters.

Friendship is a very taxing and arduous form of leisure activity.

To agree without understanding is inane. To disagree without understanding is impudent.

Wonder is the beginning of wisdom in learning from books as well as from nature.