Right angularity, acute angularity, etc., or equilaterality, which are the determinations according to which triangles are divided, do not lie in the determinateness of the triangle itself, that is, not in what is usually called the concept of a triangle, no more than in the concept of animal in general, or of mammal, bird, etc., one can find the determinations according to which animal in general is divided into mammal, bird, etc., and these classes are then divided into further genera.