The knowledge of anything, since all things have causes, is not acquired or complete unless it is known by its causes.

In God alone, essence (what He is) and existence (that he is) coincide.

Pain is a sensation produced by something contrary to the course of nature and this sensation is set up by one of two circumstances: either a very sudden change of the temperament (or the bad effect of a contrary temperament) or a solution of continuity.

The world is divided into men who have wit and no religion and men who have religion and no wit.

Those who deny the first principle should be flogged or burned until they admit that it is not the same thing to be burned and not burned, or whipped and not whipped.

An ignorant doctor is the aide-de-camp of death.

When you do not know the nature of the malady, leave it to nature do not strive to hasten matters. For either nature will bring about the cure or it will itself reveal clearly what the malady really is.

The different sorts of madness are innumerable.

That whose existence is necessary must necessarily be one essence.

Pure earth does not petrify, because the predominance of dryness over [i.e. in] the earth endows it not with coherence but rather with crumbliness. In general, stone is formed in two ways only (a) through the hardening of clay, and (b) by the congelation [of waters].

As to the mental essence, we find it in infants devoid of every mental form.