[Editor's footnote 49: If what has been said in the preceding note is correct, it is a very inadequate view of the purpose for which a generic or specific name is predicated of any subject, to say that it is in order that "the more comprehensive name may be substituted for the less comprehensive, so that each of our marks may answer the purpose of marking to as great an extent as possible." The more comprehensive and the less comprehensive name have each their uses, and the function of each not only could not be discharged with equal convenience by the other, but could not be discharged by it at all. The purpose, in predicating of anything the name of a class to which it belongs, is not to obtain a better or more commodious name for it, but to make known the fact of its possessing the attributes which constitute the class, and which are therefore signified by the class-name. It is evident that the name of one class cannot possibly perform this office vicariously for the name of another.--_Ed._] {166} We have already, also, taken notice of the artifice, by which smaller classes are formed out of larger, by the help of secondary marks. Of these secondary marks, the principal classes are designated by the terms _Differentia_, _Proprium_, _Accidens_. No very distinct boundaries, are, indeed, marked by these terms; nor do they effect a scientific division; but, for the present purpose, the elucidation of the end to which Predication is subservient, they are sufficient. _Differentia_ is always an Attributive, applicable to a Genus, and which, when combined with it, marks out a Species; as the word _rational_, which is applicable to the Genus _animal_, and when applied to it, in the phrase "rational animal," marks out a Species, and is synonymous with the word _man_. In a similar manner the word _sensitive_ is applicable to _body_, and marks out the subordinate Genus, _animal_.