Interpretations from the past 30 years of frege's explanation of the cognitive value of identity sentences are considered. Frege's explanation, Which the author finds superior to any of these interpretations, Is that 'a=b' has greater cognitive value than 'a=a' because, Given that 'a' and 'b' are different sign-Types, The sense of 'a' "may" (though it need not) differ from that of 'b'. It is pointed out that this interpretation of frege shows that his problem with identity sentences can be resolved (...) prior to the larger problem of explicating the notion of sense. (shrink)

In lieu of an abstract, here is a brief excerpt of the content:Russell's external world: 1912-1921 by Ronald E. Nusenoff IN "The Relation of Sense-data to Physics",lOur Knowledge ofthe External World,2 and "The Ultimate Constituents ofMatter",3 Russell presents a phenomenalistic reduction ofphysical objects. On this theory, the external world becomes a physical space of six dimensions, which must be logically constructed by a three-dimensional ordering of three-dimensional phenomenal spaces. In what follows, we will consider Russell's varying views, from causal realism (...) in The Problems of Philosophy,4 through phenomenalism, to neutral monism in The Analysis ofMind,5 on the nature ofthe external world. We will pay particular attention to the relation between physical and phenomenal space, and the status ofthe causal theory ofperception. 1. Realism (1912) In The Problems ofPhilosophy, Russell distinguishes a single "real" space ofscience from the "apparent" spaces ofperception. He begins with various cases of perceptual relativity, illusion, etc., and from these infers that those object which are immediately known to us are not the physical objects which the layman might take them to be. Rather, what are immediately known are sense-data, these being caused by, and so in some sense "corresponding" to, physical obI "The Relation of Sense-data to Physics", Scientia, 4 (1914), reprinted as Chapter VIII of Mysticism and Logic and Other Essays (London, 1918). 2 Our Knowledge ofthe External World as a Fieldfor Scientific Method in Philosophy (London, 1914). 3 "The Ultimate Constituents of Matter", Monist, 25 (1915), reprinted as Chapter VII of Mysticism and Logic. 4 The Problems ofPhilosophy (London, 1946 [lst published, 1912]). 5 The Analysis of Mind (London, 1921). 65 66 Russell, nos. 29-32 (1978) jects. Physical objects are located in "one public all-embracing physical space", while "our sense-data are situated in our private spaces, either the space of sight or the space of touch or such vaguer spaces as other senses may give us".6 Through experience, we are able to correlate these various private sense-data spaces (i.e., in so far as we can correlate experiences in one with experiences in another). What Russell does not go on to do here is define physical space in terms of private spaces. Given that (a) Space is relational rather than absolute, and (b) All that we can know about physical objects is that both they and their relations "correspond" to our sense-data and their relations, then (c) "we may assume that there is a physical space in which physical objects have spatial relations corresponding to those which the corresponding sense-data have in our private spaces".7 Our knowledge of physical space is then merely knowledge of relative position, and other features, e.g., shape, are "only supposed to correspond to the physical space so far as is required for the preservation of the order".8 On this view, the existence ofa physical space is necessitated solely by, and so is no more plausible than, the need for physcial objects. Russell's argument for accepting our "instinctive" belief that physical objects exist is less than compelling. Since this belief does not lead to any difficulties, but on the contrary tends to simplify and systemize our account of our experiences, there seems no good reason for rejecting it.9 In what follows, ~e shall see that Russell's phenomenalism is not explainable as differing from the realism found in The Problems of Philosophy merely in the rejection of this "instinctive" belief. II. Phenomenalism (1914-?) In his "Reply to Criticisms" in the Schilpp collection,IO Russell seems to deny that he ever really accepted phenomenalism. 6 The Problems of Philosophy, pp. 30-1 7 Ibid., p. 31. 8 Ibid., p. 33. 9Ibid., p. 24. 10"Reply to Criticisms", in P.A. Schilpp (ed.), The Philosophy ofBertrand Russell (Evanston and Chicago, 1944), pp. 679-741. Russell's external world 67 Mr. Boodin quotes a passage from me according to which it appears that at a certain time I thought only percepts were real. This was a technical hypothesis which I was trying to make logically adequate. II However, only a few pages earlier he had remarked: There are some who would deny that physics need say anything about what cannot... (shrink)