(3^ 



NATURE 



\August 8, 1889 



logician sets out. AH that he says here about the work 

 of analysis and synthesis might perhaps be translated by 

 a Kantian or even a Hegelian into his own philosophical 

 dialect. What our author, however, is concerned to 

 bring out is the practical motive that underlies our 

 common thought-distinctions. He shows in a striking 

 manner that there is something arbitrary in our way of 

 demarcating ".things" or "objects," though this is justi- 

 fied by practical exigencies. The recognition of this 

 elasticity in our conception of a thing enables the writer 

 later on to handle with good effect the common distinc- 

 tion between concrete and abstract terms. These, says 

 our author, are not absolute, but relative designations. 

 " Hardly any object, as objects are regarded by us, can be 

 selected, which is not to some extent a product of our 

 powers of abstraction, and the more or less of this faculty 

 called into play in any particular case hardly warrants us 

 in labelling the instances respectively with such distinct 

 designations." 



Somewhat similar considerations are applied to 

 collective terms. " There is nothing," writes Dr. Venn 

 in his most ingenious vein, " to hinder us from taking 

 a ' scratch lot ' of things, to use the slang phrase, 

 and giving a name to the lot with the caprice which 

 we show in naming a yacht or a dog," e.g. the persons 

 who happen at a particular moment to be in a given 

 space in Fleet Street. This idea of the arbitrary limits 

 of our common distinctions is made good use of in the 

 treatment of the relation of the subject and predicate 

 in propositions where, as too rarely happens in English 

 works on logic, adequate recognition is taken of im- 

 personal propositions. With reference to this last topic, 

 however, it should be said that Dr. Venn's treatment 

 thpugh fresh and suggestive, is hardly adequate. He 

 seems to start from the supposition that logicians resolve 

 all forms of predication into attribution of qualities to 

 things (the subjects). This is to ignore the careful analysis 

 of the import of propositions carried out by Mill, Bain, 

 and others. 



In a work on inductive logic the mode of dealing with 

 causation may be said to be conclusive as to the writer's 

 competence. Dr. Venn's account forms one of the most 

 valuable portions of his work. Very happy and fruitful 

 in simplification and the dispelling of confusion is his 

 idea that the logician in dealing with the relation of cause 

 and effect stands midway between the point of view of 

 every-day practical sense and that of a rigorously 

 scientific or speculative intelligence. The popular view 

 is practical, and is subordinated to the production of 

 (desirable) effects. The logician improves on this, first of 

 all by enumerating the antecedents more completely, and 

 secondly by " screwing up the cause and effect into close 

 juxtaposition," — that is, into an approximately immediate 

 sequence. At the same time, he does not aim at absolute 

 completeness in either respect, for this, as the writer 

 shows, would be to defeat his end. He retains something 

 of the popular practicality of view, and this is ingeniously 

 illustrated in the common logical doctrine that, whereas 

 the same antecedent can only be followed by one 

 consequent, the same consequent can be preceded 

 by different antecedents (plurality of causes). Per- 

 haps Dr. Venn is a little hard on Mill and logicians 

 generally for their way of formulating the causal re- 



lation. No doubt, as he contends, every concrete 

 event is a highly complex group of elements, fol- 

 lowed by another complex group. But the logician is 

 dealing with causation for purposes of induction. He 

 assumes that the investigator must generalize, and gene- 

 ralize as far possible, if he wishes to attain his goal, viz. 

 comprehensive principles or laws. A general statement, 

 such as " Friction produces heat," is, no doubt, in a sense 

 highly elliptical. There must of course be, in every case, a 

 definite set of circumstances in which the friction acts and 

 the heat is developed. But there is no need to refer to 

 these in stating the general truth ; on the contrary, this 

 statement, just because it is a large principle available 

 for guidance in a vast number of diverse cases, must be 

 an abstraction. Historically considered, moreover, it 

 may be said that Dr. Venn makes too much of the 

 practical impulse in the genesis of our idea of causation. 

 Primitive man, as soon as he could form an idea about 

 cause at all, was presumably already beginning to ask 

 about the origin of things, and to work out a crude 

 cosmogony of his own. 



On the nature of inductive processes, and the well- 

 known methods formulated by Mill, our author is dis- 

 tinctly in advance of his predecessors. With his customary 

 caution he points out the difficulties that have to be got 

 over before generalization can begin. Combining in a 

 manner the views of Mill, Whewell, and Jevons, he re- 

 gards a complete process of inductive discovery as con- 

 sisting of three steps, viz. (i) a stroke of insight or creative 

 genius in order to detect the property to be generalized 

 (and possibly also the class) ; (2) the formal process of 

 generalization ; and (3) the final stage of verification 

 (apparently by way of deduction). The chapter on the 

 methods is judiciously critical, and may with advantage 

 be compared with Mr. Bradley's less discriminating treat- 

 ment. The way is prepared for a study of the complex 

 problems of physical induction by the selection of a 

 simple artificial example, viz. the case of a man in an 

 hotel office, who has to determine what room rings a 

 particular bell. This case is dealt with by purely formal 

 considerations, similar to those which guide us in the 

 problems of symbolic logic. It is then shown that such 

 purely formal treatment is inappropriate in the case of 

 physical investigations, and the special methods of induc- 

 tion are thus introduced as a pis aller. The author is 

 most original in dealing with the Joint Method, which, 

 every careful reader of Mill's "Logic" must have felt 

 was very far from clear. 



There are other features in Dr. Venn's scheme of 

 induction which deserve careful notice. Among these 

 may be named the account of co-existences as distin- 

 guished from sequences (chapter iii.) ; the description 

 of the nature and function of units and standards] 

 (chapters xviii. and xix.), which is less technical and more j 

 suitable to a logical treatise than that given by Jevons ;.| 

 the highly characteristic chapter on the possible exten- 

 sion of our general powers of observation (chapter xxiii.), j 

 where the bold idea is entertained of our being able some' 

 day to spread out an event in time just as the telescope 

 and the microscope enable us to spread out an object 

 in space ; and, lastly, the discussion in the concluding 

 chapter of the effect of our practical tendencies in modi- 

 fying a strictly logical or speculative view of the world- 



