188 Inverse Probability. [CHAP. vn. 



tions on each side. Had one set of experiments only been 

 proposed, and had we been asked to evaluate the probability 

 of continued repetition of them confirming their verdict, I 

 should have felt all the scruples I have already mentioned. 

 But here we have got two sets of experiments carried on 

 under almost exactly similar circumstances, and there is 

 therefore less arbitrariness in assuming that their unknown 

 conditions are tolerably equally prevalent. 



18. Examples of the description commonly introduced 

 seem objectionable enough, but if we wish to realize to its 

 full extent the vagueness of some of the problems submit 

 ted to this Inverse Probability, we have not far to seek. In 

 natural as in artificial examples, where statistics are unattain 

 able the enquiry becomes utterly hopeless, and all attempts 

 at laying down rules for calculation must be abandoned. 

 Take, for instance, the question which has given rise to some 

 discussion 1 , whether such and such groups of stars are or are 

 not to be regarded as the results of an accidental distribu 

 tion ; or the still wider and vaguer question, whether such and 

 such things, or say the world itself, have been produced by 

 chance ? 



In cases of this kind the insuperable difficulty is in deter 

 mining what sense exactly is to be attached to the words 

 &amp;lt; accidental and random which enter into the discussion. 

 Some account was given, in the fourth chapter, of their 

 scientific and conventional meaning in Probability. There 

 seem to be the same objections to generalizing them out of 

 such relation, as there is in metaphysics to talking of the 

 Infinite or the Absolute. Infinite magnitude, or infinite 



1 See Todhunter s History, pp. Forbes in a paper in the Philosophi- 



333, 4. cal Magazine for Dec. 1850. It was 



There is an interesting discussion replied to in a subsequent number by 



upon this question by the late J. D. Prof. Donkin. 



