NATURE 



609 



THE LOGIC OE DARWIN. 

 The Mtihod of Danuin : a Study in Scientific Method. 

 By Frank Cramer. (Chicago : A. C. McClurg and 

 Co., 1896.) 



THIS excellent and most useful little work arose, as 

 its author states in the preface, " from the belief 

 that the direct study of scientific method, as it is illustrated 

 by the works of the accepted masters, is worthy of far 

 more careful attention than is usually accorded to it." 

 The method of Darwin was chosen for the author's 

 purpose (pp. 23, 24) because of the importance of scien- 

 tific method as a study, because " logicians and scientific 

 philosophers draw their illustrations of scientific method 

 almost exclusively from the physical sciences" which, 

 although "fascinating on account of their brilliancy and 

 their approach towards mathematical certainty," are less 

 adapted than the biological sciences "to furnish models 

 for the average student, because in the nature of their 

 logical difficulties they approach more nearly to the 

 experiences of common life," lastly because 



" Darwin's custom of presenting all sides of a case very 

 frequently led him to expose the original course of his 

 thought and the order of his discoveries [rightly regarded 

 by the author as a rare thing in a discoverer] so clearly 

 as to make the reader almost feel that he and Darwin 

 are making the discovery together. Darwin consciously 

 recognised or unconsciously felt that there was con- 

 siderable power to produce conviction in an understanding 

 of the particular mode in which the truth was reached. 

 He so habitually took the reader into his confidence that 

 he will probably always remain the clearest model in the 

 biological world for the study of applied logic." 



Having made his choice for the weighty and cogent 

 reasons which have been quoted above, the author pro- 

 ceeds to analyse Darwin's method, and the manner in 

 which he applied it, continually illustrating his argument 

 by reference to various discoveries and hypotheses — well 

 selected and briefly but sufficiently described in language 

 of great clearness and precision. The attitude of the 

 writer towards his great subject is peculiarly pleasing. 

 Although feeling the deepest respect for the "master- 

 mind" of Darwin, and proclaiming "that Darwin's 

 investigations, and the reasoning based upon them, have 

 famished the biological sciences with their dominant 

 principles," the author frankly criticises and employs as 

 illustrations any mistakes which he can find in the vast 

 researches of the great thinker of our century, and having 

 found them, attempts to explain the causes to which they 

 were due. 



The scope and object of the work may be inferred from 

 the subjects of its chapters. The first deals with " Edu- 

 cation and the Art of Reasoning " ; the second, " Darwin's 

 Views of Method"; the third, "The Starting Point of 

 Investigations " ; the fourth, " E.xhaustiveness — Time 

 given to Investigations . . ."; the succeeding four 

 chapters are devoted to " Negative Evidence," " Classifi- 

 cation," "Analogy," and "Induction" respectively; the 

 succeeding five to "Deduction"; while the fourteenth 

 contains " General Discussions"; the fifteenth, " Logical 

 NO. 1 46 1. VOL. 56] 



History of the Principle of Natural Selection "; the six- 

 teenth, " Conclusion." 



The whole volume is full of suggestive thoughts worthy 

 of the deepest attention. The exigencies of space pre- 

 vent more than a very brief selection to be made use of 

 in this place. The distmction between the reasoning 

 which follows the order of discovery, and that which 

 follows the order of proof, is very clearly expressed, 

 together with a plea, on behalf of the student, for the 

 more frequent employment of the former. " Books and 

 lectures are invariably built up on the plan of proof — the 

 question how a conclusion was reached is rarely pre- 

 sented . . ." Hence 



"the student is made a recipient. He is struck by the 

 lucid arrangement of facts, the majestic sweep of the 

 argument, and wonders why the world did not sooner 

 get hold of the truth that seems so conclusive to him. 

 In the laboratory the hand-books tell him what to look 

 for and where to find it, and in the lecture-room the 

 facts are arranged and the theoretical explanations 

 are made for him. Thus in neither of the two practical 

 divisions of the art of reasoning is he allowed to follow 

 even the untrained impulses of his intellect" (pp. 19, 20}. 



Even when the importance of the reasoning employed 

 in discovery is recognised, models of it will be found to 

 be rare because a man of science, 



" after establishing a conclusion to his own satisfac- 

 tion, is not concerned with telling other people how he 

 reached it, but with convincing them of its truth. For 

 this purpose he throws his conclusions and facts into the 

 order best suited to form a compact argument." 



This statement seems to us to be not only true, but one 

 of those truths which merely require to be pointed out in 

 order to produce an important effect. This reasoning^ 

 stated in the author's clear language, is likely to lead 

 observers to reconsider their methods of exposition, and 

 determine occasionally to attempt the not uninteresting 

 task of unravelling the tangled and devious lines by which 

 they have been led to discovery. 



The hard work, especially upon geological problem? 

 performed in all the isolation and difficulties of the voyage 

 of the Beagle., is regarded as the great educational mflu- 

 ence of Darwin's life, and the author attaches importance 

 to the fact that he was " unhampered by laboratory hand- 

 books with directions for finding the facts, or by pro- 

 fessors to do the reasoning for him, either before or after 

 the facts were found " (p. 30). 



The writer truly maintains that " the very grain of his 

 scientific character was conscientiousness " (p. 31), a view 

 which was eloquently put before the members of the 

 Junior Scientific Club at O.xford by Prof. Michael Foster 

 in one of the earliest lectures — I think the earliest — 

 delivered before that Society. 



One of the greatest of the many debts due to the 

 author is the clear statement of the meanings of the terms 

 induction, deduction, and the inductive method (pp. 35- 

 39). Darwin, as we know, was not convinced by writers 

 of a " deductive " cast ; on the other hand, Darwin's 

 friend and teacher Sedgwick accused him of forsaking the 

 "inductive method.'' Deduction has come to be a term of 

 reproach, induction a term of commendation, when applied 

 to a scientific worker. Now the work before us puts all 

 this in its true light, to the great help and comfort of 



D D 



