(2) _Secondary attention._—This casual and forced attention is not, however, what we ordinarily mean when we speak of ‘giving attention’ to something. We mean rather the sustained attention that we pay to a task, a lecture, a puzzle; we often mean an attention that goes against the grain, in which _we_ seem to do the forcing, holding our mind by main force upon a tedious and uninteresting subject. Is not this secondary attention very different from primary attention? Let us see. If you think how many sense-organs man has, all of them open to manifold stimulation at the same time; and if you think, further, how many different lines of interest man has, all of them likely to bring up ideas of memory or ideas of imagination; you will realise that only very powerful stimuli, those that make an unescapeable biological appeal to the organism, can compel attention—that is, can thrust their sensations to the focus—as if in disregard of competition. Such stimuli are _hors de concours_; all the rest have to face their rivals. This fact gives us the answer to our question. Secondary attention is in reality nothing else than _a conflict of nerve-forces, each one of which, if it were acting alone, would make its sensation or image the most vivid bit of experience at the moment, but each one of which is continually checked and thwarted by other forces that are urging their own sensations or images to the front_. We might say, in brief, that secondary attention is a conflict of two or more primary attentions; but we must remember that the actual fighting is done in the nervous system; we shall say more of that presently. We can observe some part of this struggle; our mind wanders, our eye is caught by some chance movement and we lose the thread of our work, we surprise ourselves thinking of something else, we look at our watch to see how the hour is going; in a word, the focal processes are instable; now one and now another perception or idea becomes more vivid than the rest; and the continual shift of vividness is proof of the conflict of the underlying nerve-forces.