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SCIENCE 



[N. S. Vol. S.LIV. No. 1134 



place, science is rooted in what I have just 

 called the whole apparatus of common- 

 sense thought. That is the datum from 

 which it starts, and to which it must recur. 

 We may speculate, if it amuses us, of other 

 beings in other planets who have arranged 

 analogous experiences according to an en- 

 tirely different conceptual code — namely, 

 who have directed their chief attention to 

 different relations between their various 

 experiences. But the task is too complex, 

 too gigantic, to be revised in its main out- 

 lines. You may polish up common sense, 

 you may contradict it in detail, you may 

 surprise it. But ultimately your whole 

 task is to satisfy it. 



In the second place, neither common 

 sense nor science can proceed with their 

 task of thought organization without de- 

 parting in some respect from the strict con- 

 sideration of what is actual in experience. 

 Think again of the chair. Among the ex- 

 periences upon which its concept is based, 

 I included our expectations of its future 

 history. I should have gone further and 

 included our imagination of all the pos- 

 sible experiences which in ordinary lan- 

 guage we should call perceptions of the 

 chair which might have occurred. This is 

 a difficult question, and I do not see my 

 way through it. But at present in the con- 

 struction of a theory of space and of time, 

 there seem insuperable difficulties if we re- 

 fuse to admit ideal experiences. 



This imaginative perception of experi- 

 ences, which, if they occurred, would be 

 coherent with our actual experiences, seems 

 fundamental in our lives. It is neither 

 wholly arbitrary, nor yet fully determined. 

 It is a vague background which is only 

 made in part definite by isolated activities 

 of thought. Consider, for example, our 

 thoughts of the unseen flora of Brazil. 



Ideal experiences are closely connected 

 with our imaginative reproduction of the 



actual experiences of other people, and also 

 with our almost inevitable conception of 

 ourselves as receiving our impressions 

 from an external complex reality beyond 

 ourselves. It may be that an adequate 

 analysis of every source and every type of 

 experience yields demonstrative proof of 

 such a reality and of its nature. Indeed, it 

 is hardly to be doubted that this is the case. 

 The precise elucidation of this question is 

 the problem of metaphysics. One of the 

 points which I am urging in this address 

 is that the basis of science does not depend 

 on the assumption of any of the conclusions 

 of metaphysics; but that both science and 

 metaphysics start from the same given 

 groundwork of immediate experience, and 

 in the main proceed in opposite directions 

 on their diverse tasks. 



For example, metaphysics inquires how 

 our perceptions of the chair relate us to 

 some true reality. Science gathers up 

 these perceptions into a determinate class, 

 adds to them ideal perceptions of analogous 

 sort, which under assignable circumstances 

 would be obtained, and this single concept 

 of that set of perceptions is all that science 

 needs; unless indeed you prefer that 

 thought find its origin in some legend of 

 those great twin brethren, the cock and 

 bull. 



My immediate problem is to inquire into 

 the nature of the texture of science. Sci- 

 ence is essentially logical. The nexus be- 

 tween its concepts is a logical nexus, and 

 the grounds for its detailed assertions are 

 logical grounds. King James said, "No 

 bishops, no king. ' ' With greater confidence 

 we can say, "No logic, no science." The 

 reason for the instinctive dislike which 

 most men of science feel towards the recog- 

 nition of this truth is, I think, the barren 

 failure of logical theory during the past 

 three or four centuries. We may trace this 

 failure back to the worship of authority 



