Generalization and classification, it may be noted in passing, are two aspects of the same process of thought.  When one passes from the individual facts to the larger fact which brings them together, as in the assertion, Members of the Phi Beta Kappa are good scholars, one makes a generalization; when one asserts of an individual the larger fact, as in the assertion, My brother is a good scholar (My brother belongs to the class Good Scholars), one makes a classification.

When a classification or generalization is constant and familiar, it brings forth, by the natural economy of language, a name for the class or the principle; “federation,” “deciduous trees,” “emotion,” “terminal moraine,” are all names of classes; “attraction of gravity,” “erosion,” “degeneration,” “natural selection,” are names of principles which sum up acts of generalization.  Almost always these names begin as figures of speech, but where they are used accurately they have a perfectly exact meaning.  Darwin has given some account of this process of language: 

“It has been said that I speak of natural selection as an active power or deity, but who objects to an author speaking of the attraction of gravity as ruling the movements of planets?  Every one knows what is meant by such metaphorical expressions, and they are almost necessary for brevity:  so, again, it is difficult to avoid personifying the word ‘Nature.’  But I mean by Nature the aggregate action and product of many laws, and by laws the sequence of events as ascertained by us."[30]

When the facts intended to be meant by a phrase are thus carefully specified and delimited, the phrase ceases to be a figure of speech, and becomes the name of a class or of a principle.

Generalization and classification always take place for purposes of reasoning;[31] and reasoning which is dependent on them rests on the assumption that things are uniformly correlated in nature; when we throw things together into classes we assume that what is true for one member of a class, so far as it is a member of that class, is true to the same extent and for the purpose for which the class is made for all other members of that class.

In practice a large part of our reasoning is through generalization and classification; and as we have seen, it has a more substantial basis than when we rest on an analogy.  If you hear that your brother has been elected to the Phi Beta Kappa, you reason from the generalization that all members of the Phi Beta Kappa are high scholars to the inference that your brother must have taken high rank.  When I see a gang of carpenters knocking off work at four o’clock in the afternoon, I infer that they must belong to the union, because I know that unions as a class have established an eight-hour day.  If you were arguing that the standards for graduation from your college should be raised, you would try to show that each year enough men are graduated with