What helps in the first place to disclose a permanent object is a permanent sensation. There is a vast and clear difference between a floating and a fixed feeling; the latter, in normal circumstances, is present only when continuous stimulation renews it at every moment. Attention may wander, but the objects in the environment do not cease to radiate their influences on the body, which is thereby not allowed to lose the modification which those influences provoke. The consequent perception is therefore always at hand and in its repetitions substantially identical. Perceptions not renewed in this way by continuous stimulation come and go with cerebral currents; they are rare visitors, instead of being, like external objects, members of the household. Intelligence is most at home in the ultimate, which is the object of intent. Those realities which it can trust and continually recover are its familiar and beloved companions. The mists that may originally have divided it from them, and which psychologists call the mind, are gladly forgotten so soon as intelligence avails to pierce them, and as friendly communication can be established with the real world. Moreover, perceptions not sustained by a constant external stimulus are apt to be greatly changed when they reappear, and to be changed unaccountably, whereas external things show some method and proportion in their variations. Even when not much changed in themselves, mere ideas fall into
