406 Prof. Forbes on the evidence for a Physical Connexion 



or preconception whatever. Whence, then, this astounding 

 probability of 13130 to 1 that B shall not be within a degree 

 of A? If it express anything, what does it express? 



"J Q 1 QQ 



[13.] What the probability ——— expresses maybe thus 



illustrated*. Suppose it to be known that two comets exist at 

 once in the sky, of which one is telescopic, and its position 

 has not been indicated. The probability in question repre- 

 sents the expectation which will exist in the mind of a person 

 possessed of this partial information, that if he takes a tele- 

 scope with a field of 2° in diameter, and fixes the cross wires 

 upon the larger comet, the telescopic one shall not be some- 

 where in the field, which includes of the whole sphe- 



13131 



rical area. Mitchell's probability is therefore a significant 

 number; but it belongs to an estimation of chance totally 

 distinct from that to which he applied it; for it is evident, on 

 reflection, that the ratios or probabilities of which we have 

 been speaking have no absolute signification with reference to 

 an event which has occurred, such as the distribution of stars 

 on the celestial sphere, or the throwing of any number of dice. 

 They represent only the state of expectation of the mind of a 

 person before the event has occurred, or having occurred be- 

 fore he is informed of the result ; for that can make no differ- 

 ence on the grounds of his expectation of a given event. The 

 dice are thrown, the result is determined ; but the expectation 

 of a person as to that result is unchanged until he casts hi-s 

 eyes on the table, at which instant expectation, and all rea- 

 soning founded on chance, random, hazard, or by whatever 

 name we choose to call it, vanishes, and Certainty takes the 

 place of Doubt. The possible combinations, in respect of 

 position, of even a limited number of stars is evidently infinite ; 

 and it does appear to be an illegitimate application of mathe- 

 matics to infer the antecedent probability of any one arrange- 

 ment which experience presents us with, since but one arange- 

 ment can exist at a time. I suspect that as we narrow the 

 field of speculation by withdrawing every inference from as- 

 sumed causation, we shall have very little, if anything, to 

 reason about. I shall give an instance in illustration of my 

 meaning. 



[14.] Suppose a person wholly unacquainted with the game 

 of chess to notice a chess-board with two or more pieces stand- 

 ing upon it; will several pieces standing near to one another 

 on one part of the board give him any idea of their places being 

 * This illustration is different from that given in the original paper. 



