EVERY FORM OF MATTER in motion acting on the organs ofsense is reflected in the brain as a sensation which corresponds tothis form of movement of matter. The different forms of motion of matter (mechanical movement of

bodies, molecular oscillations in the form of heat, electrical or magnetic current, chemical dissolution and combination, organisms), acting on different sense organs phylogenetically adapted to specific forms of matter in motion, are reflected as different sensations: cutaneous, visual, auditory, olfactory, gustatory, and so on. The concept of sensations is, therefore, inextricably bound up with the concept of matter which evokes sensations and is reflected in them. As Lenin has said: ‘Matter is a philosophical category designating the objective reality which is conveyed to man by his sensations, and which is copied, photographed and reflected by our sensations, while existing independently of them.’ Lenin further formulated the proposition: ‘Sensation is an image of matter in motion. Save through sensations, we can know nothing either of the forms of substance or of the forms of motion; sensations are evoked by the action of matter in motion upon our sense organs.’2