PHILOSOPHICAL AND PSYCHOLOGICAL ASPECTS 239 



of as extending indefinitely into both past and future. 

 Suppose that a human mind could know all that had ever 

 happened in the past. One would then know only one-half 

 of the possibilities, because there would be as much time, 

 and therefore experience, yet to come. At most, one's 

 assumption that what had always happened would continue 

 to happen could rest only upon what might be termed a 

 fifty per cent experience of the possibilities. Granted that 

 far less certainty than this is good enough for practical pur- 

 poses, the theoretical situation is worth bearing in mind. 



To pursue the matter further, the difference between a 

 coincidence and a law of nature is perhaps not so funda- 

 mental as is supposed. In the case of a coincidence, there is 

 an association of phenomena sufficiently unusual to attract 

 attention. In the case of a scientific law, we have seen cer- 

 tain phenomena associated so frequently or in such a defi- 

 nite relationship that we have been led to assume their in- 

 variable association in the future. There is no necessity for 

 the continuance of a given association beyond the fact that 

 it has been always so observed or that the definiteness of the 

 relationship makes even a single case appear conclusive. 

 Thus, if you saw a red headed man on a white horse you 

 would think nothing of the circumstance. If you saw 

 another such combination a block further on, you might 

 notice the coincidence. If you saw one at every corner, you 

 would begin to suspect that it was not a mere coincidence 

 but a constant relationship. And if you had never seen 

 white horses without red haired men on their backs and 

 always at street intersections, you would elevate this group- 

 ing of related phenomena to the level of a fact, established by 

 scientific observation and to be expected in the future, just 

 as one expects present-day birds to have feathers and beaks. 

 When so formulated as to state its assumed occurrence for 

 the past, present, and future, such a fact or group of facts 

 would become a law of science. 



The foregoing illustration is drawn from the field of 



