The theory of medicine, therefore, presents what is useful in thought, but does not indicate how it is to be applied in practice-the mode of operation of these principles. The theory, when mastered, gives us a certain kind of knowledge. Thus we say, for example, there are three forms of fevers and nine constitutions. The practice of medicine is not the work which the physician carries out, but is that branch of medical knowledge which, when acquired, enables one to form an opinion upon which to base the proper plan of treatment.

Medicine is the science by which we learn the various states of the human body in health and when not in health, and the means by which health is likely to be lost and, when lost, is likely to be restored back to health. In other words, it is the art whereby health is conserved and the art whereby it is restored after being lost. While some divide medicine into a theoretical and a practical [applied] science, others may assume that it is only theoretical because they see it as a pure science. But, in truth, every science has both a theoretical and a practical side.

Leeches should be kept a day before applying them. They should be squeezed to make them eject the contents of their stomachs.

That whose existence is necessary must necessarily be one essence.

God, the supreme being, is neither circumscribed by space, nor touched by time; he cannot be found in a particular direction, and his essence cannot change. The secret conversation is thus entirely spiritual; it is a direct encounter between God and the soul, abstracted from all material constraints.

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

I [prefer] a short life with width to a narrow one with length.