The nature of logical thought has been carefully examined by an array of able writers. Their conclusions may be provisionally reported by saying that logic is a guided form of mental operation. It is not something marked off from impulse, but a progressive elaboration and differentiation of impulse. It proceeds by the affirmation of a starting-point, which is in fact a vague indication of the goal to be reached, and develops by the criticism of the material which appears in consciousness according to its relevance to the end in view. If the judge begins by wanting to settle a controversy consistently with precedents, he has indicated in advance the shadowy outline of the desired termination of his efforts. If an administrator wants to reduce complaints against his handling of the postal service, he starts with a different mental set from the judge, but, like the mental set of the latter, his first act is to bring into view the state of affairs which he hopes to find when he quits thinking. He is accustomed to guide the operations of his mind by this preliminary characterization of the terminus sought. No thinker can haul into the center of attention the material which indicates how the terminal situation is to be attained. The thinker must wait attentively for whatever appears. If he wants to deal with such a simple practical matter as getting to the railway station, and his mind continues to fill with images of the one he left behind him, his accustomed means of asserting control is to reiterate the practical end and to hope that he can “keep his mind on” taxicabs or autobusses. Alternating with periods of reiteration and expectancy and illumination are episodes of “No” and “Yes,” which evidence the existence of guided thought. It would be misleading to stop with this formal description of the characteristics of logical thinking. Logical thinking is not a hocus-pocus to be applied here and there and everywhere. The previewing of events presupposes familiarity with the sorts of events to which the previewing relates. It usually involves analysis of the contingent future in the light of analogies with the past, which is simply a means of refining general familiarity through systematic methods of inspecting reality. General knowledge of lending and borrowing must be supplemented, for many purposes, by detailed examination of the quantitative dimensions of various routines. The precise nature of the relationship between changes in the rediscount rate and the price of call money requires analysis far beyond impressionistic familiarity.