PHILOSOPHY 29 i 



we may go on to infer propositions about the extra-mental things which are the 

 exciting causes, are then dismissed as unnecessary fictions. This is the point of view 

 adopted by Prof. Alexander, according to whom there are, strictly speaking, neither 

 contents of cognition nor cognitive states or processes. The contents of the mind con- 

 sist solely of conations of various types, and the universe is thus reduced to conative 

 tendencies and the objects in which they terminate and find their satisfaction. 1 



This extreme view that presentations have no existence is not shared by all the 

 writers who exhibit the realistic tendency. Mr. G. E. Moore and Mr. Bertrand Russell 



both appear to admit their existence. Thus in the latest statement of his 

 Russet* general philosophical position ( The Problems of Philosophy, Home University 



Library) , Mr. Russell maintains that apart from the general predicates of 

 things and the relations between them, which are universal and must not be said to 

 exist, what we know is composed of minds, physical things, and sense-data, i.e. what 

 are more usually spoken of as sense-qualities, red, sweet, salt, and the like. Sense-data 

 are neither mental (processes of consciousness) nor physical. We are acquainted 

 directly with our own minds and also with sense-data. But we have no acquaintance 

 either with physical things or with minds other than our own. Any knowledge we 

 have of the minds of others or of physical things is merely knowledge of description, and 

 its possibility depends on the truth that things with which we have no acquaintance 

 can be indirectly known if it is possible to describe them in terms of sense-data with 

 which we have acquaintance. Since Mr. Russell accepts the familiar arguments against 

 the physical reality of sensible qualities, it follows on his theory that we have no acquaint- 

 ance with physical) things. I know a physical thing only by inference, as e.g. " the cause 

 of such-and-such a definite group of sense-data." This is a description obtained by a 

 combination of sense-data which I know at first hand by acquaintance with the univer- 

 sals " the " and " cause of," and with these universals I have also immediate acquaintance. 

 My acquaintance with the meaning of " the " secures that the otherwise unknown phys- 

 ical thing signified by the descriptive phrase shall be strictly individual. Thus my 

 knowledge through sense-data of physical objects is like the knowledge I have e.g. about 

 the " magnates of the Education Department," when I know that there is such a body, 

 and what it does, but have never met any of its members. For science the most im- 

 portant point in the theory of knowledge is that we can be directly acquainted with 

 relations and universals, though these entities do not properly exist. Immediate knowl- 

 edge of this kind is what we mean by a priori knowledge, i.e. knowledge which does 

 not involve awareness of any proposition about what actually exists. As the principles 

 of inference are among the relations with which we have acquaintance a priori, we are 

 able to have a derivative a priori knowledge of all truths which are deduced by correct 

 inference from a priori principles with which we are directly acquainted. This covers 

 the whole domain of the sciences of logic and pure mathematics, as, contrary to the 

 Kantian opinion, all pure mathematics can be shown to consist of propositions deduced 

 logically from premises which involve only logical concepts and relations with which 

 we are directly acquainted. It is added that we must also include under a priori knowledge 

 our direct acquaintance with the relative intrinsic worth of various goods. This is why 

 there can be a science of Ethics. The chief special work of the particular type of realism 

 represented by Mr. Russell and his associates has been done, in close connection with 

 the earlier work of mathematicians like Peano and Frege, in the field of mathematical 

 logic, with a view to the exhibition of pure mathematics as a vast body of deductions 

 from the principles of the logic of relations, first treated with due elaboration in -the third 

 volume of E. Schroder's Algebra der Logik (1895), and applied with particular thorough- 

 ness to Arithmetic in Frege's Grundgesetze der Arithmetik (1893-1903).. The unfinished 

 magnum opus of Messrs. Whitehead and Russell, Principia Mathematica (vols. i and 2, 

 1910-12), represents the latest and fullest development of logic as a calculus of relations. 



1 See the continued controversy between Prof. Alexander and Prof. Stout as to 

 the reality of presentations in the Proceedings of the Aristotelian Society, vols. for 1908-09 

 to 1911-12, and articles on the same subject in Mind for the same years.' 



