PROBABILITY AND ENTROPY 159 



considerably larger than the chance that a mix- 

 ture of oxygen and nitrogen will separate into 

 the two pure constituents. After we have learned 

 to estimate such minute chances, and after we 

 have overcome our fear of numbers which are 

 very much larger or very much smaller than 

 those ordinarily employed, we might proceed to 

 calculate the chance of still more extraordinary 

 occurrences, and even have the boldness to re- 

 gard the living cell as a result of random ar- 

 rangement and rearrangement of its atoms. 

 However, we cannot but feel that this would be 

 carrying extrapolation too far. This feeling is 

 due not merely to a recognition of the enormous 

 complexity of living tissue but to the conviction 

 that the whole trend of life, the whole process of 

 building up more and more diverse and complex 

 structures, which we call evolution, is the very 

 opposite of that which we might expect from 

 the laws of chance. 



Let us suppose that one of our shuffling 

 machines deals a hand with four aces and the 

 next time does the same thing. We say it is a 

 remarkable coincidence, but if the machine 

 keeps on making such deals we say it is not 

 "straight." Our whole application of the theory 

 of probability to thermodynamics has rested on 



