PREFACE 



This book is substantially the course of Gifford Lectures 

 which I delivered in the University of Edinburgh in 

 January to March 1927. It treats of the philosophical 

 outcome of the great changes of scientific thought which 

 have recently come about. The theory of relativity and 

 the quantum theory have led to strange new conceptions 

 of the physical world; the progress of the principles of 

 thermodynamics has wrought more gradual but no less 

 profound change. The first eleven chapters are for the 

 most part occupied with the new physical theories, with 

 the reasons which have led to their adoption, and es- 

 pecially with the conceptions which seem to underlie 

 them. The aim is to make clear the scientific view of 

 the world as it stands at the present day, and, where it 

 is incomplete, to judge the direction in which modern 

 ideas appear to be tending. In the last four chapters I 

 consider the position which this scientific view should 

 occupy in relation to the wider aspects of human ex- 

 perience, including religion. The general spirit of the 

 inquiry followed in the lectures is stated in the concluding 

 paragraph of the Introduction (p. xviii). 



I hope that the scientific chapters may be read with 

 interest apart from the later applications in the book; 

 'but they are not written quite on the lines that would 

 have been adopted had they been wholly independent. 

 It would not serve my purpose to give an easy intro- 

 duction to the rudiments of the relativity and quantum 

 theories; it was essential to reach the later and more 

 recondite developments in which the conceptions of great- 

 est philosophical significance are to be found. Whilst 

 much of the book should prove fairly easy reading, argu- 



