Voluntary attention is thus an essentially instantaneous affair. You can claim it, for your purposes in the schoolroom, by commanding it in loud, imperious tones; and you can easily get it in this way. But, unless the subject to which you thus recall their attention has inherent power to interest the pupils, you will have got it for only a brief moment; and their minds will soon be wandering again. To keep them where you have called them, you must make the subject too interesting for them to wander again. And for that there is one prescription; but the prescription, like all our prescriptions, is abstract, and, to get practical results from it, you must couple it with mother-wit. The prescription is that _the subject must be made to show new aspects of itself; to prompt new questions; in a word, to change_. From an unchanging subject the attention inevitably wanders away. You can test this by the simplest possible case of sensorial attention. Try to attend steadfastly to a dot on the paper or on the wall. You presently find that one or the other of two things has happened: either your field of vision has become blurred, so that you now see nothing distinct at all, or else you have involuntarily ceased to look at the dot in question, and are looking at something else. But, if you ask yourself successive questions about the dot,--how big it is, how far, of what shape, what shade of color, etc.; in other words, if you turn it over, if you think of it in various ways, and along with various kinds of associates,--you can keep your mind on it for a comparatively long time. This is what the genius does, in whose hands a given topic coruscates and grows. And this is what the teacher must do for every topic if he wishes to avoid too frequent appeals to voluntary attention of the coerced sort. In all respects, reliance upon such attention as this is a wasteful method, bringing bad temper and nervous wear and tear as well as imperfect results. The teacher who can get along by keeping spontaneous interest excited must be regarded as the teacher with the greatest skill.