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204 thinking these substitutions take place, for if a man is trying to compare two complicated situations, he soon finds exhausting the attempt to hold both fully in mind in all their detail. He employs a shorthand of names and signs and samples. He has to do this if he is to advance at all, because he cannot carry the whole baggage in every phrase through every step he takes. But if he forgets that he has substituted and simplified, he soon lapses into verbalism, and begins to talk about names regardless of objects. And then he has no way of knowing when the name divorced from its first thing is carrying on a misalliance with some other thing. It is more difficult still to guard against changelings in casual politics.

For by what is known to psychologists as conditioned response, an emotion is not attached merely to one idea. There are no end of things which can arouse the emotion, and no end of things which can satisfy it. This is particularly true where the stimulus is only dimly and indirectly perceived, and where the objective is likewise indirect. For you can associate an emotion, say fear, first with something immediately dangerous, then with the idea of that thing, then with something similar to that idea, and so on and on. The whole structure of human culture is in one respect an elaboration of the stimuli and responses of which the original emotional capacities remain a fairly fixed center. No doubt the quality of emotion has changed in the course of history, but with nothing like the speed, or elaboration, that has characterized the conditioning of it.

People differ widely in their susceptibility to ideas.