492 FALLACIES. 



together, are the conditions upon which the possession of inhabitants 

 is dependent, or are even marks of those conditions. Nevertheless, 

 so long as we do not know what the conditions are, they may be con- 

 nected by some law of nature with those common properties ; and to 

 the extent of that possibility the planets are more likely to be inhabited, 

 than if they did not resemble the eai'th at all. This non-assignable 

 and generally small increase of probability, beyond what would other- 

 wise exist, is all the evidence which a conclusion can derive from 

 analogy. For if we have any the slightest reason to suppose any real 

 connexion between the two properties A and B, the argument is no 

 longer one of analogy. If it had been ascertained (I purposely put 

 an absurd supposition) that there was any connexion, by causation, 

 between the fact of revolving round an axis and the existence of ani- 

 mated beings, or if there were any reasonable ground for even suspect- 

 ing such a connexion, a probability would arise of the existence of 

 inhabitants in the planets, which might be of any degree of strength, 

 up to a complete induction ; but we should then infer the fact from the 

 ascertained or presumed law of causation, and not from the analogy of 

 the earth. 



The name analogy, however, is sometimes employed by extension, 

 to denote those arguments of an inductive character, but not amount- 

 ing to a real induction, which are employed to strengthen the argument 

 drawn from a simple resemblance. Though A, the property common 

 to the two cases, cannot be shown to be the cause or effect of B, the 

 analogical reasoner will endeavor, if he can, to show that there is some 

 less close degree of connexion between them ; that A is one of a set 

 of conditions from which, when all united, B would result ; or is an 

 occasional effect of some cause which has been known also to produce 

 B; and the like. Any of which things, if shown, would render the 

 existence of B by so much more probable, than if there had not been 

 even that amount of known connexion between B and A. 



Now an error, or fallacy, of analogy may occur in two ways. Some- 

 times it consists in employing an argument of either of the above kinds 

 with correctness indeed, but oveiTating its probative force. This very 

 common aberration is sometimes supposed to be particularly incident 

 to persons distinguished for their imagination ; but in reality it is the 

 characteristic intellectual vice of those whose imaginations are ban-en, 

 either fi-om want of exercise, natural defect, or the narrowness of their 

 range of ideas. To such minds, objects present themselves clothed in 

 but few properties ; and as, therefore, few analogies between one ob- 

 ject and another occur to them, they almost invariably overrate the 

 degi'ee of importance of those few : while one whose fancy takes a 

 wider range, perceives and remembers so many analogies tending to 

 conflicting conclusions, that he is not so likely to lay undue stress upon 

 any of them. We always find that those are the gi'eatest slaves to 

 metaphoiical language who have but one set of metaphors. 



But this is only one of the modes of eiTor in the employment of 

 arguments of analogy. There is another, more properly deserving the 

 name of fallacy; namely, when resemblance in one point is inferred 

 from resemblance in another point, although there is not only no 

 evidence to connect the two circumstances by way of causation, but 

 the evidence tends positively to disconnect them. This is properly tho 

 Fallacy of False Analogies. 



