All this is clear in principle, though psychology stands sorely in need of detailed analyses. Let us add a final word of caution,—that you beware of confusing the practical or moral value of selective action with its psychological status. Napoleon the Great was an incomparably more efficient person than Dite Deuchars, and the results of his action were incomparably wider; but with a trifle more balance in the impulsive tendencies, and a little freer play of ideas, the latter gentleman could have performed selective actions of the same psychological type as Napoleon’s. There is, however, another kind of action—we may call it =volitional= action—in which _an impulse seems to come into conflict, not with another impulse, but with some idea or group of ideas that has no motor reference_. I hear my alarum-clock, and have the impulse to get up; but that impulse is definitely opposed by the idea of another half-hour’s sleep. How can an idea oppose an impulse? When Cæsar crossed the Rubicon his alternative was not another course of action, but the passive resignation of the two Gauls and the disbanding of his army; the choice lay between acting and refraining from action. How can activity and passivity thus come into conflict? The answer to these questions is given with what we said about the nervous correlates of attention (p. 109). We learned, you remember, that _nervous reinforcement and nervous inhibition go hand in hand_: neither acts without the other; but we were not able at that time to present the evidence for this belief. The evidence is twofold. We find, in experiments upon _abstraction_, that reinforcement always implies inhibition. Suppose, for instance, that the observer is shown a series of coloured figures, each one for a fraction of a second only, and that he is asked to report accurately upon the form of these visual stimuli. He can do so: but if he is then asked to report further about the colour, he can say little if anything in reply. Reinforcement of the form has brought with it inhibition of the colour. We find, again, in experiments with what is called _negative instruction_ that inhibition always implies reinforcement. Suppose that a picture is shown, and that the observer is told to utter the first word that occurs to him when he sees it, only that the word uttered is _not_ to be the name of the object pictured. He can do this, too; but the results prove that the ‘negative’ always brings in a ‘positive’; either the throat is held stiff, locked up for the time against any utterance whatever, or the instruction ‘Don’t name the object’ is translated by the observer into ‘Name a property of the object’ or ‘Name a use to which the object might be put’; inhibition of the name has meant reinforcement of throat-kinæsthesis or of some positively suggestive idea.