5. Accident.
(1) Genus and (2) Species.
Genus and species are relative terms and can best be defined together.
A genus is a term which stands for two or more subordinate classes.
A species is a term which represents one of the subordinate classes.
The genus may be subdivided into species; the species together form the genus.
To illustrate: The term man stands for five subordinate classes or species, as white, black, brown, yellow and red. “Man” is, therefore, a genus, while “white man” and “black man,” etc., are species. The term “polygon” is a genus with reference to “trigon,” “tetragon,” “pentagon,” etc., while “trigon” is a species of “polygon.”
Any given genus may be a species of some higher class. That is, “man,” which is a genus with reference to the kinds of men, is a species of the higher class “biped,” while “biped” is a species of “animal,” “animal” a species of “organized being,” “organized being” of “material being,” “material being” of “being.” But herewe stop, as there is no higher grade to which “being” can be referred. This highest genus takes the name of summum genus.
Similarly any given species may be a genus of some lower class. “White man,” for example, which is a species of “man,” is a genus of “American,” “Englishman,” “German,” “Frenchman,” etc. “American” is a genus of “New Yorker,” “Californian,” etc., while “New Yorker” is a genus of “Smith of Jamaica.” This last term is an individual and cannot be subdivided. It represents the lowest possible species and is referred to in logic as infima species.
It is obvious that the highest genus cannot become a species, neither can the lowest species become a genus.