There are four powers: memory and intellect, desire and covetousness. The two first are mental and the others sensual. The three senses sight, hearing, and smell cannot well be prevented; touch and taste not at all.

Anyone who conducts an argument by appealing to authority is not using his intelligence; he is just using his memory.

A person must have a good memory to keep the promises he has made. A person must have a strong imagination to be able to have pity. So closely is morality tied to the quality of the intellect.

Nothing strengthens authority so much as silence.

The acquisition of knowledge is always of use to the intellect, because it may thus drive out useless things and retain the good. For nothing can be loved or hated unless it is first known.

If you find from your own experience that something is a fact and it contradicts what some authority has written down, then you must abandon the authority and base your reasoning on your own findings.