352 CONCLUSION 



it will require a skilful drawing of the boundary line 

 to frustrate the development of a conflict here.* 



The philosophic trend of modern scientific thought 

 differs markedly from the views of thirty years ago. 

 Can we guarantee that the next thirty years will not see 

 another revolution, perhaps even a complete reaction? 

 We may certainly expect great changes, and by that 

 time many things will appear in a new aspect. That is 

 one of the difficulties in the relations of science and 

 philosophy; that is why the scientist as a rule pays so 

 little heed to the philosophical implications of his own 

 discoveries. By dogged endeavour he is slowly and 

 tortuously advancing to purer and purer truth; but his 

 ideas seem to zigzag in a manner most disconcerting 

 to the onlooker. Scientific discovery is like the fitting 

 together of the pieces of a great jig-saw puzzle; a 

 revolution of science does not mean that the pieces 

 already arranged and interlocked have to be dispersed; 

 it means that in fitting on fresh pieces we have had to 

 revise our impression of what the puzzle-picture is 

 going to be like. One day you ask the scientist how he is 

 getting on; he replies, "Finely. I have very nearly 

 finished this piece of blue sky." Another day you ask 

 how the sky is progressing and are told, "I have added a 

 lot more, but it was sea, not sky; there's a boat floating on 

 the top of it". Perhaps next time it will have turned out 

 to be a parasol upside down ; but our friend is still enthusi- 

 astically delighted with the progress he is making. The 

 scientist has his guesses as to how the finished picture will 

 work out; he depends largely on these in his search for 

 other pieces to fit; but his guesses are modified from time 

 to time by unexpected developments as the fitting pro- 



*This difficulty is evidently connected with the dual entry of time 

 into our experience to which I have so often referred. 



