  The view that categories are concepts is supported further in his discussion of the distinction among categories. Suárez, like the other scholastics who precede him, holds that categories are primarily diverse. This means that they share no common property or genus. Naturally, the question as to the source and nature of their diversity comes up, and Suárez discusses it in some detail. For us, the important point is the nature of the distinction among categories themselves. Suárez rejects two opinions with respect to this issue. According to one, a real distinction between the things contained under a genus is necessary (DM 39, 2, 19; 1861, 25: 515a). According to another opinion, the distinction between supreme genera must be modal, actual, and ex natura rei, and must precede in reality the operation of the mind (DM 39, 2, 20; 1861, 25:515b).