November 20, 1914] 



SCIENCE 



741 



wounds and in other ways. Wliile the course 

 usually is favorable, an epidemic described by 

 Siegel had a mortality of 8 per cent. The 

 manifestations are fever, digestive disturb- 

 ances and vesicular eruption on the lips, the 

 oropharyngeal lining (" aphthous fever ") and 

 sometimes on the skin. Where there is 

 danger of contamination of the milk with 

 the foot-and-mouth virus, thorough pasteuri- 

 zation of all milk and milk products is doubly 

 indicated. — Journal of the American Medical 

 Association. 



SCIENTIFIC BOOKS 

 Perception, Physics and Reality. By C. D. 



Broad, M.A., Fellow of Trinity College, 



Cambridge. Cambridge University Press. 



1914. Pp. xii + 388. 



The essay of Mr. Broad is the outgrowth of 

 a dissertation presented to Trinity College, 

 Cambridge, at the examination for fellowships. 

 As now published it is an enquiry into the in- 

 formation that physical science can supply 

 about the real. Evidently the speculative tend- 

 encies of recent science have attracted the 

 attention of philosophers, and to some extent 

 their envy. As Mr. Broad says : " When a 

 certain way of looking at the universe meets 

 with the extraordinary success with which 

 that of physics has met it becomes the duty 

 of the philosopher to investigate it with care; 

 for it is likely to offer a very much better 

 cosmology than his own unaided efforts can 

 do." This success is due to the fact, he 

 thinks, that most scientists start from a posi- 

 tion of naif realism. The only successful 

 rival, at the present time, to this realism is 

 the phenomenalism which has resulted from 

 the work of Mach and his followers. And 

 this phenomenalism which holds that the ob- 

 jects of our perceptions are non-existent ex- 

 cept when they are perceived is not according 

 to Mr. Broad, an adequate foundation for a 

 scientific system. He thus disapproves of the 

 modern physicists who are regarding energy 

 and electricity as entities rather than as attri- 

 butes. 



The essay begins with a discussion of the 

 arguments which have been advanced against 



nai'f realism, and after weighing the evidence 

 he comes to the conclusion " that none of 

 these arguments which are so confidently re- 

 peated by philosophers really give conclusive 

 reasons for dropping even the crudest kind of 

 realism." Since it is difficult to advance in 

 science without a belief in some law of cause 

 and effect, he next discusses the arguments 

 which philosophers have advanced against 

 causation. This is followed by chapters on 

 the arguments for and against phenomenalism 

 and the causal theory of perception. The es- 

 say closes with a comparison between New- 

 tonian mechanics and the so-called new me- 

 chanics which is based on variability of mass 

 with speed. Mr. Broad is quite conservative, 

 for while he does not say that the principles 

 of mechanics which have become classic may 

 not require revision from time to time, yet 

 " the more general laws will still be laws about 

 positions and velocities of some extended qual- 

 ity or qualities, and, as such, will be capable 

 of the same sort of defence that I have of- 

 fered for the traditional mechanical physics." 

 His opinion is not of great value to the 

 physicist who is not asking for a defence of 

 traditional mechanical physics but who is 

 much worried about the nature of " some ex- 

 tended quality or qualities " which has posi- 

 tion and velocity. He is anxious to know 

 whether it is matter, electricity or energy. 



The philosophical method of Mr. Broad is 

 that of the neo-realists and he owes much, 

 as he acknowledges, to the lectures and con- 

 versation of Mr. Bertrand Eussell. His point 

 of greatest departure from Mr. Russell's teach- 

 ing is perhaps the substitution of the crite- 

 rion of probability for certainty. This is to 

 make philosophy approach more closely to sci- 

 ence. As he says in his introduction : " I have 

 constantly put my conclusions in terms of 

 probability and not of certainty. This will 

 perhaps seem peculiar in a work which claims 

 to be philosophical. It seems to me that one 

 of the most unfortunate of Kant's ohiter 

 dicta is that philosophy only deals with cer- 

 tainty, and not with probability. So far is this 

 from being the case that to many philosoph- 

 ical questions about the nature of reality no 



