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THURSDAY, AUGUST 8, li 



EMPIRICAL LOGIC. 



The Principles of Empirical or Inditcti7>e Logic. By 

 John Venn, Sc.D., F.R.S., Fellow and Lecturer in the 

 Moral Sciences, Gonville and Caius College, Cambridge. 

 (London : Macmillan and Co., 1889.) 



THO.SE familiar with Dr. Venn's previous logical 

 writings felt sure that his new contribution would 

 at least be something very different from an ordinary 

 text-book. There is a novelty, perhaps something of a 

 quaint peculiarity, in the manner of viewing and illus- 

 trating his subject, which gives to the author's works an 

 appeara,nce of originality which might be easily confused 

 with that which is due, as in the case of such a treatise 

 as Mill's " Logic," to a radically new conception. And 

 to say this in these days, when logical text-books are 

 multiplied, and, as some would think, all the old problems 

 have been finally threshed out, is no small praise. In 

 the less frequently explored fields already traversed by 

 Dr. \^enn — the logic of probability and symbolic logic — 

 there was, of course, more room for such fresh treatment- 

 This freshness is, however, just as conspicuous in the 

 new treatise, which goes over the well-trodden ground of 

 common logic. If anybody is stupid enough to think 

 that logic is necessarily a dry subject, he may be recom- 

 mended to look into Dr. Venn's last treatise- It is brim- 

 full of shrewd observation, of apt illustration taken from 

 the least conventional sources ; more than this, it has 

 humour, and it has fancy — a logician's, of course, but of 

 a genuine quality. 



In his general stand-point the author is, as the title of 

 his book tells the expert, and as he fully discloses in his 

 introdu ctory chapter, not far from that of Mill. That is 

 to say, he is an out-and-out materialist. Logic is not, as the 

 formalist says, concerned only with the mind's thought 

 and its normal forms, but occupies itself about the relation 

 of this thought to objective fact or existence — that is, 

 about objective truth. Hence here, as with Mill, we find 

 the reference to reality running through the whole treat- 

 ment of the subject. This emphasizing of the objective 

 aspect is made sufficiently plain by the fact that, in his 

 first chapter, before taking up the common topics, terms, 

 propositions, &c., he deals at great length with the "phy- 

 sical foundations of inference," the assumptions with 

 respect to the nature of the external world with which 

 the logician sets out. In some directions, indeed, Dr. 

 Venn carries this objective reference further than Mill, and 

 with good results. Particularly valuable is the account 

 of the meaning of reality or objective truth in the case 

 of fictitious ideas, as "dragon." At the same time, 

 our author is very far from making logic a purely ob- 

 jective science in the sense in which the physical sciences 

 are objective. Having to give an account of and to pro- 

 vide rules for inference, it must at every step take into 

 account the subjective aspect as well. Thus it has to 

 consider facts so far as they are known, and, whilst it 

 insists that names are representative of real things, it no 

 less clearly contends that these names sum up and em- 

 body the amount of knowledge we happen to possess of 

 the realities at any particular time. The steady grasp of 

 Vol. XL.— No. 1032. 



this twofold aspect of the subject-matter of logic gives 

 Dr. Venn a great advantage in the treatment of details. 

 This is strikingly illustrated in his whole account of the 

 connotation of names, and the related subject, definition. 

 What a pommon name, e.g. " gold," means is of course a 

 group of qualities known to exist in certain real things ; 

 but a glance shows us that these are not all the qualities 

 that exist in the things, but only a certain pprtion of these 

 conventionally selected. So again, in dealing with hypo- 

 thetical propositions, the author turns his recognition of the 

 double aspect to good account. A hypothetical statement, 

 of the form, " If the summer is hot, the supply of water 

 will be diminished," has at once a reference to clear 

 objective fact, and to the mind's doubt or ignorance. The 

 mind's attitude of doubt is seen in the very form of the 

 supposition, "7/" the summer is hot," the objective cer- 

 tainty reveals itself in the inference confidently drawn 

 from the supposition. One may add that it is this same 

 just recognition of the equal rights of subject and object 

 in logic which accounts for his taking a more modest 

 view of induction than Mill. He tells us in his preface 

 that the title " Empirical Logic " is intended to show that 

 " no ultimate objective certainty, such as Mill, for in- 

 stance, seemed to attribute to the results of induction, is 

 attainable by any exercise of the human reason." Mill's 

 confident repose on a system of universal law has been 

 rudely handled by writers like the late Prof Green, who 

 denied his right to reach such universality on his purely 

 empirical or Humean basis. And now we have scientific 

 men like the late Profs. Clifford and Jevons, and Dr. 

 Venn, urging from Mill's own empirical stand-point that 

 experience can never guarantee such perfect universality. 



In the case of a work like the present one it is difficult 

 for the reviewer to give, by means of a few typical refer- 

 ences, the scope and gist of the argument. As already 

 hinted, it is not in any sense a new logical system. In- 

 deed, it can hardly be called a complete system at all. 

 It does not take us in an orderly, systematic manner 

 through all the well-recognized divisions of the subject. 

 Thus a large part of the domain of the common syllo- 

 gistic logic is very slightly dealt with, if at all ; no refer- 

 ence being made to the so-called laws of thought, or the 

 axioms which underlie the thinking process so far as 

 this is merely self-consistent. Nor even if we view it 

 as a treatise on inductive logic can Dr. Venn's work 

 be called complete, since some of the most important 

 matters appertaining to induction — for example, ex- 

 periment in relation to observation, the deductive 

 method, scientific hypothesis — are altogether passed by, 

 or only just referred to. In fact. Dr. Venn's volume, 

 which he tells us embodies the substance of courses of 

 lectures, must be regarded as a series of discussions of 

 some of the more important or more neglected points of 

 logic, having a certain connection from the fact that they 

 imply one maniire de voir, and the same fundamental 

 principles. This being so, one must try to indicate the 

 quality of the work by a reference to one or two of the 

 more important matters dealt with. 



To begin with the first chapter, which is an excellent 

 compact statement of the main pre-suppositions of 

 material logic, Dr. Venn has done good service in 

 showing how much work of the mind has gone to the 

 construction of the world of objects with which the 



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