xvi INTRODUCTION 



larly is neutral grey. Of course the colour is absurd — 

 perhaps not more absurd than the rest of the conception — 

 but I am incorrigible. I can well understand that the 

 younger minds are finding these pictures too concrete 

 and are striving to construct the world out of Hamil- 

 tonian functions and symbols so far removed from 

 human preconception that they do not even obey 

 the laws of orthodox arithmetic. For myself I find some 

 difficulty in rising to that plane of thought; but I am 

 convinced that it has got to come. 



In these lectures I propose to discuss some of the 

 results of modern study of the physical world which 

 give most food for philosophic thought. This will include 

 new conceptions in science and also new knowledge. In 

 both respects we are led to think of the material uni- 

 verse in a way very different from that prevailing at the 

 end of the last century. I shall not leave out of 

 sight the ulterior object which must be in the mind of 

 a Gifford Lecturer, the problem of relating these 

 purely physical discoveries to the wider aspects and 

 interests of our human nature. These relations can- 

 not but have undergone change, since our whole concep- 

 tion of the physical world has radically changed. I am 

 convinced that a just appreciation of the physical 

 world as it is understood to-day carries with it a feeling 

 of open-mindedness towards a wider significance tran- 

 scending scientific measurement, which might have 

 seemed illogical a generation ago; and in the later 

 lectures I shall try to focus that feeling and make 

 inexpert efforts to find where it leads. But I should 

 be untrue to science if I did not insist that its study is 

 an end in itself. The path of science must be pursued 

 for its own sake, irrespective of the views it may afford 

 of a wider landscape; in this spirit we must follow the 



