NOTES 449 



In an age of great acquisitiveness he was content to spare an 

 immense amount of time from his own work to the disin- 

 terested labour of abstracting for journals like the Revue 

 Semestrielle — strong in the belief that it was worth while to 

 do his share, and more than his share, of such unpaid and 

 almost unacknowledged toil for the advancement of mathe- 

 matics. His voluminous and important correspondence on 

 mathematical subjects with eminent mathematicians of all 

 nations shows, what all those who came into contact with him 

 know, that his capacity in his own chosen fields of work — mathe- 

 matical logic and the history of mathematical ideas — exerted 

 no narrowing effect on his interests ; that his fresh and un- 

 academic yet encyclopaedic knowledge of the whole field of 

 mathematical thought, and his vigorous intellect spiced with 

 an ironic but genial humour, made him one of the most stimu- 

 lating men of his day. 



Mr. Jourdain was the youngest son of the late Rev. F. 

 Jourdain, Vicar of Ashbourne, Derbyshire. He was educated 

 at Cheltenham College and Trinity College, Cambridge. He 

 held the Allen (University) Scholarship, and was a Fellow of 

 the London Mathematical Society and a member of the Mathe- 

 matical Association. 



The main lines along which Mr. Jourdain 's own contribu- 

 tions to thought were to develop are clearly traceable in one 

 of his early articles in the Monist (" On Some Points in the 

 Foundations of Mathematical Physics," vol. xviii, 1908). In 

 this paper he attempts the exact formulation of certain funda- 

 mental questions of mathematical physics, such as causality, 

 by the application of results he had previously reached in the 

 mathematical theory of aggregates {Journ. fur Math., cxxviii., 

 " On the General Theory of Functions "). Out of these con- 

 siderations there arose the reciprocal interest in mathematical 

 logic and in the philosophical foundations of science which 

 is reflected in all his later work. That double interest explains 

 how Mr. Jourdain, whilst an enthusiastic supporter of the 

 " logisticians," could yet criticise Mr. Russell's scorn for the 

 historical origins of mathematical ideas ; and how, whilst 

 approving of Poincare's insistence on the synthetic and in- 

 tuitional mode by which mathematical discovery advances, he 

 could yet claim that the final result is part of a logical objec- 

 tive, untainted by its psychological origins. For as a logician 

 he could see that " history is irrelevant to logic, that the truth 

 or falsity of a proposition is independent of the way in which 

 so-and-so discovered it " ; and, as an acute observer of the 

 origin and development of scientific conceptions, he could claim 

 that it was " as great a mistake to banish from teaching a 

 discussion of the growth of ideas as to try to build a house 



