for neither is genus more and less predicated of that of which it is the genus, nor the differences of genus according to which it is divided. For these are such as complete the definition of each thing, but the essence of each is one and the same, and neither admits of intention, nor remission; to have however a crooked or a flat nose, or to be in some way coloured, admits both of intension and remission. Since then, there are three species of difference considered,6. Some differences "per se," are such as divide genera into species, others by which the members divided, become specific. some indeed separable, but others inseparable, again, of the inseparable, some are per se, but others accidental, moreover of differences per se, some are those according to which we divide genera into species, but others according to which the things divided become specific:—thus of all such differences per se of animal as these, animated and sensitive, rational and irrational, mortal and immortal, the difference of animated and sensitive is constitutive of the essence of animal, for animal is an animated substance, endued with sense, but the difference of mortal and immortal, and that of rational and irrational, are the divisive differences of animal, for through these we divide genera into species: yet these very differences which divide the genera are constitutive and completive of species. For animal is divided by the difference of rational and irrational, and again, by the difference of mortal and immortal; but the differences of rational and mortal are constitutive of man, but those of rational and immortal of God, those again, of mortal and irrational, of irrational animals.[1] Thus also, since the differences of animate and inanimate, sensitive and void of sense, divide the highest substance, animate and sensitive added to substance, complete animal, but animate and deprived7. The same differences in one way con- of sense, form plant; since then, the same differ-
- ↑ Porphyry's definition of man, "animal rationale mortale," was adopted by Abelard, Albertus Magnus, and Petrus Hispanus, though sometimes with the saving clause, that it must be understood with reference to the Stoical notions of the gods. Aquinas first removed the genus animal rationale from the Arbor Porphy., and limited rationality to man, distinguishing angels as intellectuales. Cf. Summa, p. 1; Qu. lviii. 3; Opusc. xlviii. Tract 1. In the Aristotelian definition of man, δίπουν, the last would be regarded by him as a difference. Upon the constitutive element of generic and specific diff., see note to Cat. ch. 5; also Hill de Prædicab.
