In contradistinction to the elements of consciousness let us call any combination of such elements a psychical compound. The relation of the two to each other can be at once made clear by the examples that lie at hand. Let us return to our metronome. If we let one single beat work upon consciousness and then immediately arrest the pendulum, we have a psychical element. Such a beat cannot in general be further disintegrated if we, as can easily be done in such a case, abstract from the fact that we hear it from some special direction in space, &c. If, on the other hand, we let two beats work, they constitute at once a psychical compound. This becomes always more complex, the more such beats we combine into a row, and the more we increase this complication by different degrees of accentuation, as in the examples of 2/8 and 4/4 time described above. Such an element of consciousness as the single beat is called a sensation, a combination of elements into rhythms of more or less complicated constitution is called an idea. Even at the present time many psychologists use the word "idea" only for a complex that does not arise from direct outward impressions, i.e. only for so-called "memory images." For ideas formed by outward sense impressions they generally use the word "perception." Now this distinction is psychologically of absolutely no importance, since there are really no valid differences between memory ideas and so-called sense-perceptions. The memory ideas of our dreams are in general quite as lively as sense impressions in the waking state, and it is for this reason that they are often held to be really experienced phenomena. The word "idea" denotes well the essential characteristic of all these complexes. The idea (Greek idea) is the form or appearance of something in the outer world. In the same sense, as belonging to the outer world, we speak of the sensations and their complexes arising in our own body as organic sensations, because we locate them in out own body, e.g. the sensations of fatigue of our muscles, the pressure and pain sensations of the inner organs, &c. The relatively uniform elements of touch and organic sensations are distributed among the sensations of pressure, warmth, cold, and pain. In contra-distinction to these, the special senses of hearing, seeing, smelling, and tasting present an abundance of sensations, each of which, according to its peculiar constitution, is called a quality of sensation. Each such quality is besides variable in its intensity. We can, for example, produce a certain beat in very variable intensities, while the quality remains the same.