278 



NATURE 



[November 12, 19 14 



quate recognition. The second part of the book 

 deals principally with the chemical changes due to 

 different forms of radiation. The author sum- 

 marises his views by saying" : " The conception that 

 in photo-chemical change singular intermediate 

 complex ions, or, specifically speaking, veritable 

 latent light-images, are formed, appears the most 

 promising." 



(2) The account of photo-electric phenomena 

 given by Dr. Hughes is lucid and concise. The 

 photo-electric effect is regarded as a form of 

 ionisation by light. Most of our information as 

 to such ionisation has been derived from a study 

 of the action in the case of solids and liquids, 

 owing to the fact that in the case of gases ionisa- 

 tion is only brought about by light of extremely 

 short wave-lengths. The aim of the author 

 appears to have been to give a comprehensive 

 view of the present position of the subject. In 

 this he has been successful, though the result is 

 perhaps to mar the historical setting and to deny 

 adequate recognition to some of the earlier 

 w:orkers. Thus the work of Hallwachs and his 

 pupils on the influence of contact potential on 

 photo-electric phenomena is not referred to. The 

 "energy law" which is emphasised in this book 

 was established mainly by the experiments of the 

 author and of Richardson and Compton. It ex- 

 presses the fact that the maximum emission 

 energy of a photo-electron is a linear function of 

 the frequency of the light. This is in accordance 

 with the quantum theory of radiation developed 

 by Planck and Einstein, and first applied by W. 

 Wien (whose name is not mentioned) in connection 

 with Rontgen rays in 1907. 



Both volumes contain a subject index and an 

 index of authors. In the case of the latter volume 

 the index of authors is far from complete. 



PHILOSOPHY . 

 (i) A Theory of Civilisation. By S. O. G. 

 Douglas. Pp. 246. (London and Leipzig : T. 

 Fisher Unwin, 1914.) Price 55. net. 

 (2) Our Knowledge of the External World, as a 

 field for Scientific Method in Philosophy. By 

 B. Russell. Pp. vii + 245. (London and 

 Chicago : The Open Court Publishing Co. , 

 1914.) Price 75. 6d. net. 

 (i) \ READABLE and well-informed treatment 

 2\ of civilisation viewed as the outcome 

 of religious belief. The various "psychic illu- 

 sions " are considered — Olympianism, Orphism, 

 Christianity, Islam, Buddhism, the ancient reli- 

 gion of Peru, etc. — and it is argued that each 

 religion has elements which tend to an advance 

 NO. 2350, VOL. 94] 



in civilisation, these elements being always irra- 

 tional, for the rational and critical and selfisli 

 elements furnish no driving power except as to 

 the individual's own well-being. In course of 

 time disillusionment comes about ; the beliefs are 

 gradually abandoned as the intellectual powers — 

 which have grown with the civilisation — assert 

 themselves critically, and there is then a slide 

 down until civilisation and the general intelligence 

 reach such a level of degeneracy that another 

 "psychic illusion " becomes possible. The process 

 then repeats itself ; though the author apparently 

 thinks that the crest of each civilisation-wave is, 

 on the whole, higher than the last, the " spirit of 

 evolution " selecting for each successive illusion 

 that which will yield improved results. The in- 

 teresting question naturally arises as to whether, 

 after Christianity, we shall manage to get along 

 without illusions at all, or whether a new illusion 

 will impose itself, as before. The author inclines 

 to the latter opinion, but wisely refrains from 

 detailed prophecy. 



(2) This volume contains Mr. Russell's Lowell 

 Lectures, delivered in Boston last March and 

 April. They deal with the various idealisms — 

 Platonic, Berkeleyan, Bradleyan, etc.^ — as the title 

 implies, but there is also some acute criticism of 

 Bergson's intuitionism, and a full analysis of the 

 old problems of Achilles and the tortoise, and the 

 impossibility of the moving arrow's motion. The 

 author maintains the fresh and brilliant yet easy 

 style which always makes his writings a pleasure 

 to read, and though, as he says, philosophy in 

 becoming more scientific inevitably becomes less 

 humanly interesting, it is likely to retain devotees 

 as long as it has such exponents as Mr. Russell. 



The book is, of course, mainly logical, and the 

 modern position is maintained. "The trivial 

 nonsense embodied in this [Aristotelian] tradition 

 is still set in examinations, and defended by 

 eminent authorities as an excellent ' pro- 

 paedeutic,' i.e. a training. in those habits of solemn 

 humbug which are so great a help in later life " 

 (P- 33)- 



"The old logic put thought in fetters, while 

 the new logic gives it wings. It has, in my 

 opinion, introduced the same kind of advance 

 into philosophy as Galileo introduced into physics, 

 making it possible at last to see what kinds of 

 problems may be capable of solution, and what 

 kinds must be abandoned as beyond human 

 powers. And where a solution appears possible, 

 the new logic provides a method which enables 

 us to obtain results that do not merely embody 

 personal idiosyncrasies, but must command the 

 assent of all who are competent to form an 

 opinion" (p. 59). 



