152 Measurement of Belief. [CHAP. vi. 



28. We may conclude, then, that the limits within 

 which we are thus able to justify the amount of our belief 

 are far more extensive than might appear at first sight. 

 Whether every case in which persons feel an amount of 

 belief short of perfect confidence could be forced into the 

 province of Probability is a wider question. Even, however, 

 if the belief could be supposed capable of justification on its 

 principles, its rules could never in such cases be made use of. 

 Suppose, for example, that a father were in doubt whether 

 to give a certain medicine to his sick child. On the one 

 hand, the doctor declared that the child would die unless the 

 medicine were given ; on the other, through a mistake, the 

 father cannot feel quite sure that the medicine he has is the 

 right one. It is conceivable that some mathematicians, in 

 their conviction that everything has its definite numerical 

 probability, would declare that the man s belief had some 

 value (if they could only find out what it is), say nine- 

 tenths ; by which they would mean that in nine cases out of 

 ten in which he entertained a belief of that particular value 

 he proved to be right. So with his belief and doubt on 

 the other side of the question. Putting the two together, 

 there is but one course which, as a prudent man and a good 

 father, he can possibly follow. It may be so, but when (as 

 here) the identification of an event in a series depends on 

 purely subjective conditions, as in this case upon the degree 

 of vividness of his conviction, of which no one else can judge, 

 no test is possible, and therefore no proof can be found. 



29. So much then for the attempts, so frequently 

 made, to found the science on a subjective basis ; they can 

 lead, as it has here been endeavoured to show, to no satisfac 

 tory result. Still our belief is so inseparably connected with 

 our action, that something of a defence can be made for the 

 attempts described above ; but when it is attempted, as is 



