It has been proven through numerous experiments (Fere, Binet, Mosso, Janet, Newbold, etc.) that "unconscious sensations"[160] act, since they produce the same reactions as conscious sensations, and Mosso has been able to maintain that "the testimony of consciousness is less certain than that of the sphygmograph." But the particular instance of invention is very different; for it does not merely suppose the adaptation to an end which the physiological factor would suffice to explain; it implies a series of adaptations, corrections, rational operations, of which nervous activity alone furnishes us no example.[161] 2. The psychological theory is based on an equivocal use of the word consciousness. Consciousness has one definite mark--it is an internal event existing, not by itself, but for me and insofar as it is known by me. But the psychological theory of the unconscious assumes that if we descend from clear consciousness progressively to obscure consciousness, to the subconscious, to the unconscious that manifests itself only through its motor reactions, the first state thus successively impoverished, still remains, down to its final term, identical in its basis with consciousness. It is an hypothesis that nothing justifies. No difficulty arises when we bear in mind the legitimate distinction between consciousness of self and consciousness in general, the former entirely subjective, the latter in a way objective (the consciousness of a man captivated by an attractive scene; better yet, the fluid form of revery or of the awaking from syncope). We may admit that this evanescent consciousness, affective in nature, felt rather than perceived, is due to a lack of synthesis, of relations among the internal states, which remain isolated, unable to unite into a whole. The difficulty commences when we descend into the region of the subconscious, which allows stages whose obscurity increases in proportion as we move away from clear consciousness, "like a lake in which the action of light is always nearing extinction" (in double coexisting personalities, automatic writing, mediums, etc.). Here some postulate two currents of consciousness existing at the same time in one person without reciprocal connection. Others suppose a "field of consciousness" with a brilliant center and extending indefinitely toward the dim distance. Still others liken the phenomenon to the movement of waves, whose summit alone is lighted up. Indeed, the authors declare that with these comparisons and metaphors they make no pretense of explaining; but certainly they all reduce unconsciousness to consciousness, as a special to a general case, and what is that if not explaining?