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 FBIEDEICH JODL, Lehrbuch der Psychologic. 239 methods'and results. On the other hand, the questions of principle are very carefully treated with critically cautious appreciation of the conflicting opinions. No final conclusion is reached, but inci- dentally there is some effective criticism of the view which denies the possibility of any measurement of the intensities of sensations on the ground that sensations are not multiples, as also of Wundt's interpretation of the psychophysical law as merely a special case ,pf the law of the relativity of apperception. The other point is the acceptance of " extensity " as a characteristic of sensations and the vigorous advocacy, in the elaborate treatment of the visual sensations, of the essentially intuitive character of our space per- ceptions as against those who regard them as an association or fusion of optical with other sensations, or as a product of the mingling of sensations proper w r ith unconscious inference. The third dimension is included with the others in the original sense- datum. Indeed, the author goes so far as to assert that our most primitive visual sensations are spatially arranged (rdumlich geordnet, p. 553) and that we have a sensation of our eye as the point to which ah 1 the perspective lines and surfaces that run out into the third dimension from the place we happen to be in converge (p. 341). These statements could hardly be supported by facts, nor are they demanded by the exigencies of theory. The original ex- tensity of the visual sensations should be by all analogy a latent or merged plurality out of which the space relations proper are developed on the basis of many co-operating experiences, not tri- dimensional space, as such. The implication of the third dimension in the primitive visual sensation is argued for, however, as a matter of principle, on the ground of the original opposition in conscious- ness of subject and object, and the original excentric projection of sensations : functions, it is claimed, which cannot be learned, though they may be perfected and developed. If now, it is argued, the optical impression is necessarily externalised, then there can never possibly be any moment when the ego and the visual sur- face so to say coincide, and a reference to depth, however imperfect, must lie in our most primitive optical experience. This law of excentric projection is referred to again in the chapter on the ego and the external world as a refutation, on psychological grounds, of subjective idealism. But if, as is also claimed, these functions are the result of a long process of evolution adapting inner to outer relations, then again, on the general analogy of ontogenetic de- velopment, we should expect that the human infant would go through a process, though, to be sure, a relatively rapid process of acquiring them, and in that case doubt would be thrown on the original experience, whatever analysis may detect in that which comes later. But into this later experience enter the residua of past processes, and in regard to the excentric projection of sensa- tions especially, whether interpreted as externalisation or as bodily localisation, there is good reason for believing that, however the disposition may be preformed in the inherited constitution, its