fication as well as in an organization of what we have received from without. All processes of reasoning, and so all original discoveries in science and in philosophy, all speculations, theories, dogmas, controversies, and not only these complex processes, but, as we shall see, even simple judgments, commonplace beliefs, momentary acts of attention, involve such independent reaction upon the material furnished to us from without. The nature of this reaction we are further to examine.
Let us consider simpler forms of knowledge. Sense-impressions constantly suggest to us thoughts; in fact, we have few thoughts that are not either immediately suggested by sense-impressions, or else sustained in their course by a continuous stream of suitable sense-impressions. To carry on even a train of abstract reasoning, sense-impressions either present or repeated seem necessary as supports. But when sense-impressions come to us, what transforms them into thought?
The answer is, First of all, attention, an active mental process. The sense-impression is itself not yet knowledge. A sense-impression to which we give no attention slips through consciousness as a man’s hand through water. Nothing grasps and retains it. Little effect is produced by it. It is unknown. You cannot even tell what it is. For to know what such an unnoticed impression is would be to pay attention to it. But let us now consider some familiar examples of the working of attention. A simple instance will bring home to us how the boundaries of our consciousness are crowded with un-
