58 INTRODUCTION TO SCIENCE 



in the street does to get at the facts; he is not 

 content with sporadic knowledge, but will have 

 as large a body of facts as he can get; he systema- 

 tizes these data and his inferences from them, and 

 sums up in a generalization or formula. In all 

 this he observes certain logical processes, certain 

 orders of inference, and we call this scientific 

 method. 



THE LOGIC OF SCIENCE. Of modes of inference 

 there are no more than there were in the days of 

 Aristotle, who recognized three: (a) from particu- 

 lar to particular (analogical reasoning), (6) from 

 particulars to general (inductive reasoning), (c) 

 from general to particular (deductive reasoning). 

 Let us take a few examples. 



(a) Analogical Reasoning. The geologist tells 

 us the story of the making of the earth and 

 describes what happened millions of years ago, 

 and in many cases he relies on analogical reason- 

 ing. From the consequences of particular happen- 

 ings to-day he infers the efficient causes of events 

 that happened in the Devonian age. He sheds 

 the light of the present on the dark abysses of 

 the past. 



When Darwin argued from the particular vari- 

 ations which he observed in his domesticated 

 pigeons and cultivated plants to variations which 

 might have occurred in unthinkably distant aeons, 

 he was trusting to analogical reasoning. Often 



