32 WHAT IS SCIENCE? 



really is universal. Accordingly, in defining science as 

 the study of judgments concerning which universal 

 agreement can be obtained, we are limiting science to 

 judgments which affect action and deliberately excluding 

 matters which, though they may actually be the subject 

 of universal agreement, do not affect action. This con- 

 clusion is important, because it enables us to separate 

 science clearly from pure mathematics and logic ; but 

 space cannot be spared to pursue this line of thought 

 beyond a bare reference to it. 



A man may also fail to join in the general agreement, 

 not because he is lying, because he is suffering from some 

 hallucination. This possibility was noticed before 

 (p. 22), and then we distinguished hallucinations from 

 true sensations by the fact of the agreement of others. 

 But now we are applying the test of agreement much more 

 strictly, and the mere fact that the man is under an 

 hallucination and does not agree with others is sufficient 

 to make the test fail. However, the difficulty can be 

 overcome in exactly the same way as that arising from 

 lying. We study all the man's actions, and we usually 

 find that, while some of them are consistent with his 

 assertion that he does not agree, others are inconsistent 

 with that assertion ; and those that are inconsistent are 

 those which we know, from our own internal experience, 

 to be less directly connected with consciousness and less 

 liable to aberration. Our test, once more, is always 

 whether the man acts on the whole as we should act if 

 we shared the thoughts which he professes. Curious 

 instances of this nature have occurred in actual science ; 

 there have been people who professed to be able to see 

 or to hear or to feel things which other men could not see 

 or hear or feel. But so far the difficulty has always been 

 removed by setting " traps," even if the honesty of the 

 man is beyond doubt, and showing that his actions in 

 general are not consistent with his professions. 



