The Art of Medicine

The third, however, is made from the dissolution of a definition.

A definition is a statement that explains the nature and force of a thing, which gathers into one those things that are inherent in a thing, by which it separates and distinguishes it from others. H Those things that are inherent in a thing either constitute the substance or adhere to it as accidents. Genus and substantial differences constitute the substance, taken entirely from the same class, if possible. I call them substantial differences, not only those that are taken from the genus of substance, but also those that explain the nature of the thing, from whatever genus they may have originated; for here the name of substance extends broadly to any thing considered in itself. Therefore, we are accustomed to calling even accidents that have been abstracted from their subjects and considered in themselves "substances," such as disease and fever. Therefore, if we wish to find the differences and species of the things to be defined, it is necessary to know the reasoning and notion of each highest genus. A

Therefore, once the thing to be defined is proposed, it must be considered from which class it is taken, then its proximate genus must be found. This will happen if you divide the highest genus into near genera until you arrive at the species to be defined. We will teach the method of dividing shortly.