(_ii_) The working over of a vague and more or less casual idea into coherent and definite form is impossible without a pause, without freedom from distraction. We say "Stop and think"; well, all reflection involves, at some point, stopping external observations and reactions so that an idea may mature. Meditation, withdrawal or abstraction from clamorous assailants of the senses and from demands for overt action, is as necessary at the reasoning stage, as are observation and experiment at other periods. The metaphors of digestion and assimilation, that so readily occur to mind in connection with rational elaboration, are highly instructive. A silent, uninterrupted working-over of considerations by comparing and weighing alternative suggestions, is indispensable for the development of coherent and compact conclusions. Reasoning is no more akin to disputing or arguing, or to the abrupt seizing and dropping of suggestions, than digestion is to a noisy champing of the jaws. The teacher must secure opportunity for leisurely mental digestion. [Sidenote: A typical central object necessary] (_iii_) In the process of comparison, the teacher must avert the distraction that ensues from putting before the mind a number of facts on the same level of importance. Since attention is selective, some one object normally claims thought and furnishes the center of departure and reference. This fact is fatal to the success of the pedagogical methods that endeavor to conduct comparison on the basis of putting before the mind a row of objects of equal importance. In comparing, the mind does not naturally begin with objects _a_, _b_, _c_, _d_, and try to find the respect in which they agree. It begins with a single object or situation more or less vague and inchoate in meaning, and makes excursions to other objects in order to render understanding of the central object consistent and clear. The mere multiplication of objects of comparison is adverse to successful reasoning. Each fact brought within the field of comparison should clear up some obscure feature or extend some fragmentary trait of the primary object. [Sidenote: Importance of types]