SCIENCE 381 



contrary, the external criterion has to be vouched for by 

 something again external to it, we should have to go on 

 in that way for ever, or else rest at last in something 

 which was self-evident. It will be plain, on reflection, 

 that nothing external no common consent of mankind, 

 no amount of testimony, no experimentation or evidence 

 of the senses could ever take the place of an ultimate 

 criterion of truth, since some judgment of our own mind 

 must always decide for us with respect to the existence 

 and value of such criteria. Self-evidence, then, is really 

 the only possible ultimate test of truth, and must be 

 accepted under pain of complete intellectual paralysis. 

 It is incapable of demonstration, since it depends on 

 nothing else. It is continually made use of as a matter 

 of course and without reflction, and is relied on con- 

 stantly by every one who reasons. We have said that 

 self-evidence must be accepted under pain of complete 

 intellectual paralysis, because if it be not accepted, we 

 are logically reduced to absolute scepticism that is, to 

 utter folly. 



It is necessary that the student should recognise 

 the fact that we are all of us certain of something. 

 Although sincere inquiry, and therefore doubt, are not 

 only legitimate but necessary in science, nevertheless 

 reason shows us that doubt must have its limits. There 

 is such a thing as legitimate certainty, otherwise there 

 would be no certain science of any kind. But if there 

 is such a thing as legitimate certainty, then to doubt 

 about it must be illegitimate doubt. But, as we all 

 know, credulity is common to children and to weak- 

 minded, or ignorant, men and women ; therefore 

 .extreme scepticism may, at first sight, seem to be an 

 exceptionally intellectual state of mind. Nevertheless 

 a little reflection will show that it is, in fact, an excep- 



