On searching for the reason why such various experiences are expressed by the use of one word, Mr. Fullerton discovers that the common notion which unites them is the idea of similarity. But how can we speak of similarity when strictly only one thing is in question? The answer given is that we have "a series of experiences, beginning with one in which two objects are recognised as similar and yet are very clearly distinguished as two objects, continued in others in which the sense of duality falls more and more into the background, and ending in one in which there is no consciousness of duality at all." The last of these experiences is not wholly different from the others. It differs from them "not in the element which has led us to declare two objects similar—the element which they have in common—but in that which has led us to declare them two and different. It is by adding to this last experience, so to speak, that we get the others. They contain it and more." The experience in which two things are not distinguished, is at the bottom of all our experiences of similarity. The use of the expression "X is X," then, emphasises the fact that one is not to pass from X to any Y or Z, and it, moreover, puts a period to one's thinking, and fixes the thought upon X alone. When the words "identity" and "sameness" are intended to be used with some degree of precision, the former word indicates "sameness in which there is no consciousness of duality, or in which the consciousness of duality has fallen into the background and may easily be overlooked." More than half of Mr. Fullerton's work is occupied by an historical and critical consideration of the use of the word _same_ in a wrong sense, beginning with Heraclitus and coming down to Prof. W. K. Clifford. The examples he has given of that confusion of thought justifies the assertion of "the need of much greater care and exactitude than one commonly finds in metaphysical reasonings," and at the same time the hair-splitting for which Mr. Fullerton needlessly considers himself called on to plead guilty. Ω. INDUCTION AND DEDUCTION. WITH OTHER ESSAYS. By _Constance C. W. Naden_. Edited by R. Lewins, M. D. London: Bickers & Son.