_A Natural Group is steadily fixed, though not precisely limited; it is given in position, though not circumscribed; it is determined, not by a boundary without, but by a central point within;--not by what it strictly excludes, but by what it eminently includes;--by a Type, not by a Definition._ (VIII. 2.) XCIV. _The prevalence of Mathematics as an element of education has made us think Definition the philosophical mode of fixing the meaning of a word: if_ (_Scientific_) _Natural History were introduced into education, men might become familiar with the fixation of the signification of words by_ Types; _and this process agrees more nearly with the common processes by which words acquire their significations._ (VIII. 2.) XCV. _The attempts at Natural Classification are of three sorts; according as they are made by the process of_ blind trial, _of_ general comparison, _or of_ subordination of characters. _The process of Blind Trial professes to make its classes by attention to all the characters, but without proceeding methodically. The process of General Comparison professes to enumerate all the characters, and forms its classes by the_ majority. _Neither of these methods can really be carried into effect. The method of Subordination of Characters considers some characters as_ more important _than others; and this method gives more consistent results than the others. This method, however, does not depend upon the Idea of Likeness only, but introduces the Idea of Organization or Function._ (VIII. 2.) XCVI. _A_ Species _is a collection of individuals, which are descended from a common stock, or which resemble such a collection as much as these resemble each other: the resemblance being opposed to a_ definite _difference._ (VIII. 2.) {23} XCVII. _A_ Genus _is a collection of species which resemble each other more than they resemble other species: the resemblance being opposed to a_ definite _difference._ (VIII. 2.) XCVIII. _The_ Nomenclature _of a Classificatory Science is the collection of the names of the Species, Genera, and other divisions. The_ binary _nomenclature, which denotes a species by the_ generic _and_ specific _name, is now commonly adopted in Natural History._ (VIII. 2.) XCIX. _The_ Diagnosis, _or Scheme of the Characters, comes, in the order of philosophy, after the Classification. The characters do not_ make _the classes, they only enable us to_ recognize _them. The Diagnosis is an Artificial Key to a Natural System._ (VIII. 2.) C. _The basis of all Natural Systems of Classification is the Idea of Natural Affinity. The Principle which this Idea involves is this:--Natural arrangements, obtained from_ different _sets of characters, must_ coincide _with each other._ (VIII. 4.) CI.