THE APPLICATIONS OF SCIENCE 177 



applied ; the irregularity that occurs in the study of the 

 weather or of heredity is an irregularity in such events. 

 Moreover, when science uses the conception of events 

 governed by chance, it means something much more 

 definite than is associated with that word by popular 

 use. We say in ordinary discourse that an event is due 

 to pure chance when we are completely ignorant whether 

 it will or will not happen. But complete ignorance 

 can never be a basis for knowledge, and the scientific 

 conception of chance, which does lead to knowledge, 

 implies only a certain limited degree of ignorance 

 associated with a limited degree of knowledge. It is 

 impossible here to discuss accurately what ignorance 

 and what knowledge are implied, but it may be said 

 roughly that the ignorance concerns each particular 

 happening of the event, while the knowledge concerns 

 a very long series of a great number of happenings. Thus, 

 scientifically, it is an even chance whether a penny falls 

 head or tail, because while we are perfectly ignorant 

 whether on each particular toss it will fall head or tail, 

 we are perfectly certain that in a sufficiently long series 

 of tosses, heads and tails will be nearly equally dis- 

 tributed. 



When, therefore, science finds, as in the study of 

 weather or of heredity, phenomena which show some 

 regularity, but not complete regularity, it tries to analyse 

 them into perfectly regular laws acting on " chance " 

 material. And the first step in the analysis is always to 

 examine long series of the phenomena and to try to 

 discover in these long series regularities which are not 

 found in the individual members of them ; the regularity 

 will usually consist in each of the alternative phenomena 

 happening in a definite proportion of the trials. When 

 such regularity has been found, a second step can some- 

 times be taken and an analysis made into strict laws 

 applied to events which are governed by the particular 



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