INDUCTION IN ITS VARIOUS SENSES 45 



final step, by which we reach a scientific knowledge of those facts 

 in the observation of which the whole process had its origin. 1 



The method here outlined is recognized by Mill : 2 he calls it 

 &quot; deductive,&quot; admitting its application only to the more complex 

 phenomena due to a combination of causes ; yet he is forced to 

 allow that it is to this method &quot; the human mind is indebted for 

 its most conspicuous triumphs in the investigation of nature &quot;. 3 

 The advocacy of this method by many of our more recent induc 

 tive logicians, Bosanquet, Sigwart, Welton, Joseph, etc., is a 

 wholesome reaction against the Empiricism of the school of Mill. 



The various steps indicated above will form the subject-matter 

 of subsequent chapters. The whole process, however, is based 

 upon certain fundamental principles and postulates which call for 

 explanation and justification at the outset (Chaps. III. and IV.). 

 With an example 4 to illustrate the inductive process, and a com 

 parison of the latter with deductive inference, we may conclude 

 the present chapter. 



&quot; Let a chemist take some hydrogen, a gas without colour, taste, or smell ; 

 which burns with an intensely hot bluish flame ; which is 14-4 times lighter 

 than air, 23-326 litres weighing 2 grammes. Let him take another and very 

 different sort of gas, chlorine ; of a yellowish colour and an unpleasant, 

 suffocating smell ; density 2-44, weighing 35-5 times more than hydrogen, 

 22-326 litres weighing 71 grammes. 



&quot; Let the chemist mix those two gases in a glass vessel, and place it in the 

 sunlight : a violent combination will suddenly take place, disengaging 22 

 thermal units or calories of heat ; after which the chemist finds in the vessel a 

 new body, whose distinctive properties have acquired for it the name of hydro 

 chloric acid. This new body will attack most of the metals and combine with 

 them to form various salts ; it will combine with the aqueous vapour of the 

 atmosphere to form a colourless, acid solution, etc. 



&quot; So far he has observed a fact [first step]. Next, how is it to be explained ? 

 Why did it happen ? What is its cause ? He supposes that it is due to some 

 law of nature [second step] ; he supposes the formation of hydrochloric acid 

 to be due to some property inherent in those two gases, acting in certain con 

 ditions, still to be determined. This suspicion of his is an hypothesis, which he 

 must now proceed to verify. 



&quot; For this latter purpose [third step] he will multiply and vary his ex 

 periments. For example, he will let the sunshine act on a mixture of chlorine 

 and oxygen ; supposing a priori that they too will combine ; but he finds that 

 they will not. It is not every two gases, therefore, that will combine under the 

 action of the sunlight. But, perhaps, at least any quantities whatever of 

 hydrogen and chlorine will combine ? A priori, again, the supposition is 

 permissible ; but again it is negatived by the facts. For repeated experiments 



1 C/. 252: Regressive Demonstration. 7 Logic, iii., xi. and xlv. 



3 ibid, xi., 3. 4 From Mercier s Logiqtie, pp. 300 iqq. 



