Croton, approx. 500 B.C.

Crotonian. Pythagorean philosopher, physician and physicist. He was a personal student of Pythagoras. He is counted among those who had the good fortune to know the great teacher closely and to work with him. Wanting to show the limited horizon of human knowledge, the philosopher observes from the beginning of his book that, while the gods have clear knowledge of the invisible and visible world, humans can only draw conclusions from their observations. It is clear that Alcmaeon intended to speak in his book (of which only a few fragments have survived) about things that belong to the visible human world and not to the invisible. Thus, his teaching was apparently limited to the area of ​​medicine, physiology and psychology.

Alcmaeon is the first to recognize the brain as the central organ to which all the senses are connected. The difference between man and animals is that man understands, while they only feel.

His interest in medicine and physiology led him to formulate some remarkable views on health and disease: "Alkmeon asserts that health is the balance of forces, i.e. having equal rights in the body for the wet, the dry , the cold, the warm, the bitter, the sweet and the rest, but the monarchy between them, that is, the individual dominance of one of them, creates the disease.. But health is the symmetrical mixing of the qualities". The living body is a system in which the basic constituent forces, even if opposed to each other, must be equal. When these are balanced, the system works harmoniously. Harmony is disturbed when a force gains power beyond its normal measure. The disharmony that is then caused is disease. The remedy, then, which means restoring the balance, which has been disturbed, consists in restoring to order the power that violated the principle of equal rights within the small "republic" of the body.

Alcmaeon still attempted to give a rational explanation of the physiological fatigue of the living organism and its death. He explained the body's course towards old age and death as a consequence of a series of changes constantly occurring within it. The line of biological time traced by every living organism is not cyclical and recycled, but rather a linear march forward with no return. If old age were another childhood, humans and other animals could live forever, since the course of their lives would be a cycle, where the end would be a new beginning and life would be repeated eternally anew. Everything, then, that is born and lives is necessarily led to death, because the beginning here cannot be attached to the end.