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.

Medicine considers the human body as to the means by which it is cured and by which it is driven away from health.

Now it is established in the sciences that no knowledge is acquired save through the study of its causes and beginnings, if it has had causes and beginnings; nor completed except by knowledge of its accidents and accompanying essentials.

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

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.