SCIENCE AND NATURE 29 



not, and there cannot be, universal agreement about it 

 or indeed any agreement at all. For I am alone in the 

 room and nobody but myself has ever had, or can ever, 

 have, any share in that experience. Accordingly our 

 definition of science excludes that experience of mine 

 from the judgments which science studies, although to 

 common sense it was certainly an event in the external 

 world. 



Such a simple example indicates at once how very 

 much stricter than the common-sense criterion of extern- 

 ality is the criterion which must be satisfied before any 

 experience is admitted by our definition as part of the 

 subject-matter which science studies. Science, as we 

 shall see, really does maintain the criterion strictly, 

 while common sense is always interpreting it very loosely. 

 I do not mean to assert that common sense is wrong to 

 apply a less strict criterion that is a question which 

 lies far outside our province ; all that I mean is that any 

 experience which fails to satisfy the strict criterion of 

 universal agreement, though it may be quite as valuable 

 as experience which does satisfy it, does not form part 

 of the subject-matter of science, as we are considering it. 

 Here is the distinction between modern science and the 1 

 vaguer forms of primitive learning out of which it grew. 

 When the possibility of applying the strict criterion of 

 universal agreement was realized, then, for the first time 

 in the history of thought, science became truly scientific 

 and separated itself from other studies. All the early 

 struggles of science for separate recognition, Bacon's 

 revolt against mediaeval learning and the nineteenth- 

 century struggle of the " rationalists " against the 

 domination of orthodox theology, can be interpreted, as 

 we shall see, as a demand for the acceptance of the strictly 

 applied criterion of universal agreement as the basis for 

 one of the branches of pure learning. 



