366 TRANSMISSION 



The successions of red and black representing gain and loss 

 are so irregular and so confusing that the player fails to detect 

 the ratio of more than 5 per cent that is against him, and con- 

 sequently does not realize that the longer he plays the more 

 certain are his losses. Nor does he realize that in the long run 

 nothing is more absolutely certain than the law of chance. The 

 deviation is not great at any point after the first few throws, 

 and herein lies the first deceptive quality of all games of chance. 



If the letters of the word " incomprehensibility " be tossed 

 into the air in such a manner that they must fall into a line, the 

 chances of their falling in the proper order to spell the word 

 correctly are exceedingly remote, yet it is bound to happen if the 

 trials are long enough continued. 



These simple facts teach us not to attach too much impor- 

 tance to occasional occurrences, however strange or apparently 

 improbable. They teach us, too, that there may be no special 

 cause at the bottom of the occurrence beyond the mathematical 

 law of probability. The tossing of coins shows why it is, for 

 example, that every theory for the control of sex that ever has 

 been or ever can be invented has been repeatedly verified. 

 There is but one alternative, and every assumption of cause, 

 however absurd, is certain to come true (?) half the time, which 

 is sufficient proof for most people who depend upon memory 

 impressions rather than upon absolute records. 



Proof by the method of instance is therefore extremely 

 hazardous. Something more than the mere fact of coincidence 

 is necessary in order to establish a causative relation with any 

 very high degree of certainty. 



When, therefore, a deformity in a child corresponds to a muti- 

 lation in a parent we are not warranted in at once assuming a 

 causative relation. We are to remember that deformities of all 

 kinds are comparatively common; that mutilations are exceed- 

 ingly so ; that frequently a mutilation will resemble a natural 

 deformity or an injury ; and that occasionally, under the laws of 

 probability, the mutilation of the parent will resemble the 

 deformity in the offspring, thus suggesting direct transmission. 

 We are to remember, too, that the law of chance must first be 

 satisfied before we can assume causation. 



