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JOSEPH PETXOLDT, Philosophic der Reinen Erfaliruny. 393 in this way ; and (2) that if they did the fact of the unity of consciousness would be inexplicable. The proof of the first point is much simplified by the fact that the direct determining means of a mental act are to be found only in the immediately preceding mental acts (p. 65). Mr. Petscoldt shows that there is no such thing as the determination of psychical states by their immediate antecedents. Indeed all the elements requisite for such determination are lacking. There is no continuity in the mental life. For continuity to exist (p. 60) two members of a series must become more like each other the nearer they are to each other within the series, and the successive parts of the series must pass imperceptibly into each other. Now the mental life is just made up of sharp transitions (int i/i'i-adezu cms laitter Plotzlichkeiten ziisammenyesetzt), and resembles nothing so much as the changes in a kaleidoscope. This discontinuity is implied in Weber's law. As the stimulus is continuously increased, we become conscious only at discon- tinuous intervals of differences in sensation. ' It was a complete misconception of this relation,' says Mr. Petzoldt (p. 60), ' when Fechner transferred mathematical symbols and methods devised to interpret the continuous changes of mathematical functions to the interpretation of discontinuous psychical changes.' Further, mental processes are not bound down to a single direction. Such singleness of direction is found only when a natural process left to itself invariably takes place only in one of two equally thinkable opposite directions. But we can repeat the number-series backwards almost as fluently as we can repeat it forwards. As for uniqueness of determination, even in strictly logical thinking as in the attempt to work out a problem of Euclid, or to deduce the conclusion from a syllogism, one idea does not call forth without fail some one idea and no other. There is a certain dependence here no doubt between the suc- cessive ideas, but it is not unideterminate. In the associations of fancy and imagination there is still less unideterminateness Two associated ideas may, as a rule, appear in consciousness together, but it cannot be said that the one determines the presence of the other according to a law. There is then neither continuity, singleness of direction, nor uniqueness in the sequences of the mental life. This is the direct testimony of the facts themselves. As a very strong indirect witness to the same conclusion we have the fact that the unity of consciousness is incompatible with the notion of this unideter- mination of one state of consciousness by another. By unity of consciousness Mr. Petzoldt means the continuous time-identity of the individual consciousness. It consists in the recognition of my previous experiences as mine. This recognition implies that any idea can appear in consciousness either simultaneously with any other idea or percept, or immediately before or after it. For an idea or experience can only be said to be mine so far