600 c. STUMPF'S TONPSYCHOLOGIE, i. when the internal conditions are added. Much the same line of remark might be followed with respect to the author's conception of relations of difference &c. among sensations. In a manner, of course, the difference is independent of our observation. That is to say, there are the conditions present for the perception of dif- ference, supposing the supplementary internal conditions are added. These conditions involve a certain amount of difference in the stimuli concerned ; and the simple recognition of this fact (whether its interpretation be physical or psycho-physical) at once gives us a solution to the puzzle about all sensations of pitch becoming one sensation with which the author, showing an excess of ingenuity not unprecedented in his writings, perplexes his unwary reader. It may be added that Dr. Stumpf, in his opposition to the relativism of Bain, Wuudt and others, seems to fall into the other extreme of absolutism. To him the particular content of a sensation is something wholly independent of any reference to other sensations. This again in a manner is true, namely, that the physiological process concerned involves a tendency to a sensation of a particular kind and serves to deter- mine its content. But here again the question may be asked: Would this content ever be realised apart from references more or less distinct to other sensations ? Or to put it in the form selected by Dr. Stumpf : Could a child have a definite sensation of colour or tone the first time the corresponding nerve-centre was stimu- lated in the way implied ? Does not a definite sensation involve, in close connexion with the act of attention which is its internal condition, a number of rapid half -developed references to past sensations, and does not this group of references help to give it its particular definiteness? Dr. Stumpf 's idea of a definitely qualified sensation in itself out of relation to observant mind, and of an absolute sensational unit out of relation to other sensations, may perhaps be justified as a kind of mathematical fiction, of great service for his special purposes, namely, measurement of sense-judgment and its factors, but it hardly seems likely that he would be content with this view of its function. A few words must suffice to indicate the scope of the Second Part. This, as already remarked, deals with the relations of successive tones. Judgments as to quality are first dealt with, apparently as those most easily obtainable, after which are handled judgments respecting intensity. Throughout this Part, save where the author makes an incursion into the domain of general principles, we have the results of special lines of scientific inquiry brought together and explained. The idea of distance as applied to a series of qualitatively unlike contents as tones is unfolded at great length. Of particular interest is the employ- ment of mediate criteria in judging of tone-qualities. The author gives many experiences, a number of which were obtained by himself, tending to show that the muscular sense plays a less important part in judging of the pitch of tones than is commonly
