[Footnote 3: Some logicians, however, speak of defining a thing, and illustrate this as if by a thing they meant a concrete individual, the realistic treatment of Universals lending itself to such expressions. But though the authority of Aristotle might be claimed for this, it is better to confine the name in strictness to the main process of defining a class. Since, however, the method is the same whether it is an individual or a class that we want to make distinct, there is no harm in the extension of the word definition to both varieties. See Davidson's _Logic of Definition_, chap. ii.] [Footnote 4: See Davidson's _Logic of Definition_, chap. iii.] CHAPTER II. THE FIVE PREDICABLES.--VERBAL AND REAL PREDICATION. We give a separate chapter to this topic out of respect for the space that it occupies in the history of Logic. But except as an exercise in subtle distinction for its own sake, all that falls to be said about the Predicables might be given as a simple appendix to the chapter on Definition. Primarily, the Five Predicables or Heads of Predicables--Genus, Species, Differentia, Proprium, and Accidens--are not predicables at all, but merely a list or enumeration of terms used in dividing and defining on the basis of attributes. They have no meaning except in connexion with a fixed scheme of division. Given such a scheme, and we can distinguish in it the whole to be divided (the _genus_), the subordinate divisions (the _species_), the attribute or combination of attributes on which each species is constituted (the _differentia_), and other attributes, which belong to some or all of the individuals but are not reckoned for purposes of division and definition (_Propria_ and _Accidentia_). The list is not itself a logical division: it is heterogeneous, not homogeneous; the two first are names of classes, the three last of attributes. But corresponding to it we might make a homogeneous division of attributes, as follows:-- Attributes ___________|____________ | | Defining Non-defining _____|______ ____|__________ | | | | Generic Specific Proprium Accidens (Differentia)