July 21, 1921] 



NATURE 



643 



and we are far from this at present — is that we 

 -cannot expect complete success in anti-tuberculosis 

 work until we are in a position to say that "we 

 are exercising- complete supervision over, and 

 making provision for, the whole of the sick life 

 of the consumptive, whether he is trending to- 

 wards complete recovery or towards death." 

 There is not a single community in Great Britain 

 concerning which that statement can be affirmed. 

 The nearest approach to it is what is known as 

 the Framingham experiment, which has been 

 ^oing on for four or five years in a small town in 

 Massachusetts, and of which a valuable account 

 has been published by the American Tuberculosis 

 Association. It is to be hoped that a full account 

 •of this experiment, and the results which have 

 been obtained, will form part of the proceedings 

 of the forthcoming conference in London. 



The Foundations of Physics. 



Physics : The Elements. By Dr. Norman R. 

 Campbell. Pp. ix + 565. (Cambridge : At the 

 University Press, 1920.) 405, net. 



DR. CAMPBELL has attempted with great 

 courage a very ambitious task — that of 

 ■discussing critically the fundamental conceptions, 

 propositions, and methods of the science of 

 physics. A rough idea of the nature of his work 

 may be given by saying that he attempts to do 

 for the foundations of physics what Peano, 

 Whitehead, Russell, and others of the modern 

 ■critical school have done for the central principles 

 •of mathematics. The spirit, however, rather than 

 the exact method of these mathematical philo- 

 sophers is what he emulates, for, apparently, one 

 ■of the factors which determined him to write this 

 book was a lively dissatisfaction caused by the 

 fact that hitherto all inquiry of this nature in 

 physics has been carried out by mathematicians 

 rather than by experimenters. Mach, of course, in 

 spite of Dr. Campbell's implication, was an ex- 

 perimenter of note, as well as a mathematician 

 .and philosopher, but our author aspires to a some- 

 what more complete and general discussion than 

 that carried out by Mach for certain branches of 

 physics, and wishes to include recent develop- 

 ments. Again, he is more anxious to win the 

 •confidence of the man in the laboratory (who, as 

 he says, is often " not merely uninterested in 

 fundamental criticism, but positively hostile to 

 it "), while at the same time desiring to meet the 

 logicians on their own ground, if not with their 

 own weapons. From a window in his study he 

 looks down with sympathy upon the laboratory, 

 NO. 2699, VOL. 107] 



and writes with one eye on the bust of Mr. 

 Bertrand Russell, serene above the conflict, and 

 with the other on the working physicist, who is 

 cursing alternately his electrometer and the 

 theory of errors. 



Dr. Campbell reaUses clearly that the physicist 

 is not necessarily either logical or consistent when 

 he is most efficient. This realisation is an im- 

 portant feature of the book, and distinguishes the 

 author from his predecessors. "It is undoubted," 

 he says, " that we can study science with perfect 

 satisfaction to ourselves . . . although we commit 

 the heinous offence of using ambiguous terms. 

 And this fact is simply an indication that we do 

 not use in the course of our study any processes 

 which require words to be unambiguous." "Il- 

 logical is not synonymous with erroneous." 

 Again, he insists more strongly upon the funda- 

 mental importance of analogy than do most, 

 writers on the principles of science, contending^ 

 that analogies are not so much aids to the estab- 

 lishment of theories— the usual view — as essential 

 parts of the theories. The theories are systematic 

 expressions of analogies. Here, we think, he 

 will not only interest all physicists, but also carry 

 them with him. On the other hand, his dis- 

 cussion of such points as how we can define, say, 

 silver, and his conclusion that all logical diffi- 

 culties can be avoided by stating "silver exists," 

 will not, possibly, appeal to the experimenter. 

 The experimenter has never felt the need of a 

 formal definition of his materials ; Dr. Campbell 

 agrees, but labours the point at considerable 

 length, whereas the question of modern concep- 

 tions of isomers and isotopes, which will 

 bear much discussion, receives little attention. 



The book before us (the preface informs us that 

 further volumes have been contemplated) is 

 divided into two parts, one dealing with the pro- 

 positions of science, and the other with measure- 

 ment. The first consists in the main of a discussion 

 of the nature of laws, hypotheses, and theories, of 

 what is meant in physics by these terms, and of 

 the possibility of obtaining more or less formal 

 definitions of them. Dr. Campbell's debating 

 often tends to show the difficulty of arriving at 

 conclusions rather than to lead us to convincing 

 conclusions — a fact attributable to the difficultv of 

 the subject. For instance, he suggests that the 

 decision as to whether a given proposition is or 

 is not a law has to be left to the judgment of 

 serious students of science — which is sound, but 

 not sensational. Throughout the book the word 

 "important" plays a large part, and obviously 

 to reduce a question to terms of relative import- 

 ance is to raise fresh points. The discussion of 



