If a person studies too much and exhausts his reflective powers, he will be confused, and will not be able to apprehend even that which had been within the power of his apprehension. For the powers of the body are all alike in this respect.

Astrology is not an art, it is a disease.

It is thus necessary to examine all things according to their essence, to infer from every species such true and well established propositions as may assist us in the solution of metaphysical problems.

The people who are abroad are all those that have no religion, neither one based on speculation nor one received by tradition. Such are the extreme Turks that wander about in the north, the Kushites who live in the south, and those in our country who are like these. I consider these as irrational beings, and not as human beings; they are below mankind, but above monkeys, since they have the form and shape of man, and a mental faculty above that of the monkey.

The key to the understanding and to the full comprehension of all that the Prophets have said is found in the knowledge of the figures, their general ideas, and the meaning of each word they contain.

The risk of a wrong decision is preferable to the terror of indecision.

Astrology is a disease, not a science... It is a tree under the shadow of which all sorts of superstitions thrive. ... Only fools and charlatans lend value to it.