Many phenomena that belong here escape ordinary observation, because their continuous repetition makes us insensitive to them. In those cases where an impression was accompanied by a very strong feeling-tone, and where its return is accompanied by a totally different affective state, we notice distinctly how the original feeling-tone becomes modified owing to the changed background. Thus every psychical process possesses its specific tone, even if it appears as a mere repetition of a previous process. The changing secondary ideas, by means of their own affective influences, give it its special temporal and local signs. By means of these each single process can be distinguished from any other, however similar this may be. The opposite phenomenon may also occur. Who does not know the strange feeling which occasionally comes over us at some process, the feeling that we have already in the past experienced this thing, although we know with certainty that this is in reality impossible? These phenomena also belong to the department of feelings, and we must connect them with the influences which arise from the indistinct secondary ideas, and which may at times almost exactly correspond, even when the chief ideas themselves are absolutely different. If such feelings become particularly strong, they very likely exert a reactive influence upon the assimilation process, and thus cause the new experience to appear as the repetition of a previous one. It may be that the so-called "second sight," which some people imagine they possess, depends upon very strong individual affective reactions of this kind and their assimilative influences. The ever-changing constellations of secondary ideas give each single experience its specific feeling-tone, by means of which it is distinguished from previous and following experiences. So it may happen that similar constellations of the darkly perceived content return in processes that otherwise are different, i.e. in the components that stand in the focus of consciousness. There is also another experience that may be mentioned here--one that has certainly escaped no keen observer of his own psychical life. If one calls to mind any previous experience, or in general any previous period of life--e.g. any definite period of one's childhood, of one's student life, or the beginning of one's professional career, &c.--each such striking experience or each such period of life is connected with a peculiar feeling, which also in this case enters into a distinct reciprocal action with the recalled ideas, inasmuch as it raises them to a greater degree of clearness and is itself increased by them. Any single recalled idea could scarcely account for the unusual intensity and the specific quality which these feeling-tones often reach. We must also remember that a clearly apperceived content in such cases seldom arises, and that in the second set (the periods of life) we have not as a rule one single idea.