Know that for the human mind there are certain objects of perception which are within the scope of its nature and capacity; on the other hand, there are, amongst things which actually exist, certain objects which the mind can in no way and by no means grasp: the gates of perception are closed against it.

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.

All forces that reside in the body are angels.

WHEN reading my present treatise, bear in mind that by "faith" we do not understand merely that which is uttered with the lips, but also that which is apprehended by the soul, the conviction that the object [of belief] is exactly as it is apprehended. If, as regards real or supposed truths, you content yourself with giving utterance to them in words, without apprehending them or believing in them, especially if you do not seek real truth, you have a very easy task as, in fact, you will find many ignorant people professing articles of faith without connecting any idea with them.

The more we desire for that which is superfluous, the more we meet with difficulties; our strength and possessions are spent in unnecessary things, and are wanting when required for that which is necessary.

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 more necessary a thing is for living beings, the more easily it is found and the cheaper it is; the less necessary it is, the rarer and dearer it is.