158 THE SCIENCE OF LOGIC 



regard to the action of the virus which were based upon facts did not lose 

 their value ; they simply had to be revised by the aid of the new light shed 

 upon the question.&quot; l 



&quot; A pari&quot; &quot; a fortiori&quot; and &quot; a contrario &quot; arguments, are all 

 arguments from analogy : &quot; The planet Mars bears a close re 

 semblance to our earth, therefore, a pari, it is probably inhabited &quot;. 

 &quot; Work in the mines is hard on the health of male adults ; there 

 fore, a fortiori, it is injurious to women and children.&quot; &quot; The 

 abuse of alcohol is a cause of national decay ; therefore, a con 

 trario, the suppression of that abuse will make for national 

 prosperity.&quot; 



Inference by analogy is a very common form of reasoning, and 

 very liable to abuse ; the real significance of resemblances may 

 be misinterpreted : and the metaphorical use of language often 

 increases this danger. Some examples of inconclusive analogies 

 will be examined in the section on fallacies. 2 



The characteristic which we seek to prove of an observed 

 phenomenon, by analogy, may be known to belong to a single 

 other phenomenon, or to a whole class. More usually, perhaps, it 

 is something we suspect or know to be true of a whole class, 

 something embodied in a generalization or law, which law we 

 now seek to extend to the newly observed phenomenon. Or, 

 we may have in our minds only the two individual phenomena ; 

 but even here the inference which Aristotle calls TrapaSeisffjia, 

 Example is not made from particular to particular without the 

 aid of an implicit generalization. &quot; The inference is the same,&quot; 

 remarks Aristotle, 3 &quot;whether it be based on resemblance to one 

 case or to many &quot; (193). 



236. THE &quot;ARGUMENT FROM EXAMPLE&quot; IN ARISTOTLE. 

 By the Argument from Example Aristotle meant an inference 

 from one individual phenomenon to another similar phenomenon 

 &quot; by bringing the one under the same universal to which the 

 other is known to belong &quot;. 4 Manifestly, therefore, the Aristotelean 

 TrapdSeiyfAo, is what we now commonly call inference from 

 analogy. Comparing it with the inductive syllogism (207), he 

 describes it as &quot; proving the major term of the middle by a term 

 resembling the minor&quot; * This description he explains and justifies 



l op. cit., p. 325. a C/. also JOSEPH, op. cit., pp. 494 sqq. 



3 Anal. Prior., ii., 24 [21], (3). 



* Anal. Prior., ii., 24 [26], (4) : Qa.vtp bv oZcSri rb TrapaStiyfid tanv . . . us ptpoi 

 wpbs ntpes, orav &fi&amp;lt;j&amp;gt;u ftitv $ uwb ravr6, yvupi/ioy tf Odrfpor. Cf. sdsoRhet. i., 2, (15)- 

 (I?) I ii- 20. 



ibid. 



