In short, pains should be taken to see that the object on which thought centers is _typical_: material being typical when, although individual or specific, it is such as readily and fruitfully suggests the principles of an entire class of facts. No sane person begins to think about rivers wholesale or at large. He begins with the one river that has presented some puzzling trait. Then he studies other rivers to get light upon the baffling features of this one, and at the same time he employs the characteristic traits of his original object to reduce to order the multifarious details that appear in connection with other rivers. This working back and forth preserves unity of meaning, while protecting it from monotony and narrowness. Contrast, unlikeness, throws significant features into relief, and these become instruments for binding together into an organized or coherent meaning dissimilar characters. The mind is defended against the deadening influence of many isolated particulars and also against the barrenness of a merely formal principle. Particular cases and properties supply emphasis and concreteness; general principles convert the particulars into a single system. [Sidenote: All insight into meaning effects generalization] (_iv_) Hence generalization is not a separate and single act; it is rather a constant tendency and function of the entire discussion or recitation. Every step forward toward an idea that comprehends, that explains, that unites what was isolated and therefore puzzling, generalizes. The little child generalizes as truly as the adolescent or adult, even though he does not arrive at the same generalities. If he is studying a river basin, his knowledge is generalized in so far as the various details that he apprehends are found to be the effects of a single force, as that of water pushing downward from gravity, or are seen to be successive stages of a single history of formation. Even if there were acquaintance with only one river, knowledge of it under such conditions would be generalized knowledge. [Sidenote: Insight into meaning requires formulation] The factor of formulation, of conscious stating, involved in generalization, should also be a constant function, not a single formal act. Definition means essentially the growth of a meaning out of vagueness into _definiteness_. Such final verbal definition as takes place should be only the culmination of a steady growth in distinctness. In the reaction against ready-made verbal definitions and rules, the pendulum should never swing to the opposite extreme, that of neglecting to summarize the net meaning that emerges from dealing with particular facts. Only as general summaries are made from time to time does the mind reach a conclusion or a resting place; and only as conclusions are reached is there an intellectual deposit available in future understanding. [Sidenote: Generalization means capacity for application to the new]