One and the same thing can at the same time be good, bad, and indifferent, e.g., music is good to the melancholy, bad to those who mourn, and neither good nor bad to the deaf.

I should attempt to treat human vice and folly geometrically... the passions of hatred, anger, envy, and so on, considered in themselves, follow from the necessity and efficacy of nature... I shall, therefore, treat the nature and strength of the emotion in exactly the same manner, as though I were concerned with lines, planes, and solids.

Pride is over-estimation of oneself by reason of self-love.

Love is nothing but joy accompanied with the idea of an eternal cause.

I have tried sedulously not to laugh at the acts of man, nor to lament them, nor to detest them, but to understand them.

Men are mistaken in thinking themselves free; their opinion is made up of consciousness of their own actions, and ignorance of the causes by which they are determined.

Do not weep; do not wax indignant. Understand.