The greatness of a life can only be estimated by the multitude of its actions. We should not count the years, it is our actions which constitute our life.

To love is to be delighted by the happiness of someone, or to experience pleasure upon the happiness of another. I define this as true love.

Nihil est sine ratione. There is nothing without a reason.

Thus God alone is the primary Unity, or original simple substance, from which all monads, created and derived, are produced.

According to their [Newton and his followers] doctrine, God Almighty wants to wind up his watch from time to time: otherwise it would cease to move. He had not, it seems, sufficient foresight to make it a perpetual motion. Nay, the machine of God's making, so imperfect, according to these gentlemen; that he is obliged to clean it now and then by an extraordinary concourse, and even to mend it, as clockmaker mends his work.

The art of discovering the causes of phenomena, or true hypotheses, is like the art of deciphering, in which an ingenious conjecture often greatly shortens the road.

Every present state of a simple substance is the natural consequence of its preceding state, in such a way that its present is big with its future.