Who makes this selection among the memory-images? The stimulus itself, which rouses the brain-cells into activity. Naturally those cells would be the most strongly excited which are directly connected with the afferent nerves. Somewhat weaker is the excitement of the cells to which the cell first excited sends its impulse by way of the customary nerve channels; still weaker the excitement of those cells which, by the same mechanism, receive their stimulus from the secondarily excited cell. That idea will be the most powerful, therefore, which is awakened directly by the perception itself; somewhat weaker that which is aroused by the first impression through association of ideas; weaker still that which the association in its turn involves. We know further that a phenomenon never produces a single stimulus, but several at once. If, for example, we see a man before us, we do not merely perceive a single point in him, but a larger or smaller portion of his exterior, _i.e._, a large number of differently coloured and differently illuminated points; perhaps we hear him as well, possibly touch him, and, at all events, perceive besides him somewhat of his environment, of his spacial relations. Thus, there arise in our brain quite a number of centres of stimulation, operating simultaneously in the manner described above. There awakes in consciousness a series of primary presentations, which are stronger, _i.e._, clearer, than the associated or consequent representations, namely, just those presentations which the man standing before us has himself aroused. They are like the brightest light-spots in the midst of others less brilliant. These brightest light-spots necessarily predominate in consciousness over the lesser ones. They fill the consciousness, which combines them in a judgment. For what we call a judgment is, in the last resort, nothing else than a simultaneous lighting up of a number of presentations in consciousness, which we in truth only bring into relation with each other because we ourselves became conscious of them at one and the same moment. The ascendency which the clearer presentations acquire over the more obscure, the primary presentations over derived representations, in consciousness, enables them, with the help of the will, to influence for a time the whole brain-activity to their own advantage, viz., to suppress the weaker, _i.e._, the derived, representations; to combat those which cannot be made to agree with them; to reinforce, to draw into their circuit of stimulation, or simply to arouse, others, through which they themselves are reinforced and secure some duration in the midst of the constant emergence and disappearance of representations in their pursuit of each other. I myself conceive the interference of the will in this struggle for life amongst representations as giving motor impulses (even if unconsciously) to the muscles of the cerebral arteries. By this means