According to Galen, there are three states of the human body: health - that is, a state in which the human body by nature and by the combination of particles is such that all actions emanating from it are performed healthily and completely. Illness is a state of the human body, the opposite of this, and the third state, according to Galen, is neither health nor illness - either due to the lack of complete health and complete illness, as happens, for example, with the body of old people, convalescents and children, or due to coincidence of both states simultaneously in two organs or one organ, but in two categories far from each other, such as when an organ is healthy in relation to nature, but sick in relation to the combination of particles, or in one organ and in categories close to each other, as, for example, when an organ is healthy as regards shape, but not healthy as regards size and position, or healthy as regards passive qualities, but not healthy as regards active qualities.
And sometimes this condition arises from the fact that health and illness follow each other at different times, such as when someone is healthy in winter and sick in summer.
Diseases can be simple or complex. A simple disease is a disease that is one of the varieties of the disease of nature or one of the varieties of the disease of combinations of particles, which we will talk about later. A complex disease is one in which two or more of these varieties are combined, merging into one disease.
Let's start first of all with simple diseases and say:
There are three types of simple diseases. The first kind is diseases attributed to organs that are similar in terms of particles, that is, diseases from a disorder of nature. They are classified as organs that are similar in terms of particles because they primarily and essentially occur in organs that are similar in terms of particles, and only because of this they affect complex organs. Such diseases can form and become present in any organ that is similar in terms of particles, whereas this is impossible for complex diseases.
The second type is diseases of organs and instruments. These are diseases of combinations of particles that arise in organs composed of organs that are similar in terms of particles and are instruments of action. The third kind is general diseases that happen to organs that are similar in terms of particles, but also happen to organs-tools, since they are organs-tools, without the appearance of such diseases in organs-tools following their appearance in organs similar regarding particles. Such, for example, are diseases called “disruption of continuity” and “disintegration of the whole.” Disruption of continuity sometimes occurs with an articulation, without at all affecting the organs that are similar in terms of particles that make up the articulation, and sometimes occurs, for example, with only nerves, bones and blood vessels.
In general, there are three kinds of diseases - diseases following a disorder of nature, diseases following a disorder of the image of a combination of particles, and diseases following a violation of continuity. Every disease follows one of these phenomena, derives from it and is attributed to it. The diseases of disturbed nature are well known; there are sixteen of them, and we have already talked about them.