GENUS

(Gr. γένος) refers first to the principle of generation (Gr. γένεσις), the genus or stock, then to the multitude of things springing from one principle. In logic genus refers first to the universal that is predicable of many things differing in species; like species, it answers the question "What is it?" Whereas species predicates the whole essence, genus predicates the common and determinable part of the essence of its subject. The genus that is contained under no higher genus is called supreme genus or category. Those contained under higher genera are called subaltern genera.

In Aristotelian dialectics genus is one of the four predicates, constituting one kind of dialectical problem (Topica 101b 37–102b 27; 128b 14–139a 20). Genus refers also to the genus subjectum of a science, the limited subject-matter considered by a given science (Anal. post. 76b 11–16).

In things composed of matter and form, matter is remotely the principle of genus inasmuch as it is the principle of all potency. It is also the principle of diverse genera within a category, insofar as in the category of substance matter receives the perfection of act to different degrees. As actuated to one degree, say "sensitive life," it will be the basis of a genus and be in potency either to the further perfection, "rational," or to the imperfection, "non-rational" (St. Thomas Aquinas, In Boeth. Trin., 4.2).

The genus of the logician is, moreover, to be distinguished from the genus of the natural philosopher. The former looks merely for a common ratio, the latter requires in addition a common matter (physical genus).

See Also: predicables; porphyrian tree; definition; matter and form.

[w. baumgaertner]