FALLACIES OF GENERALIZATION. 553 



[only] be effected by the copious administration of absorbent and testa- 

 ceous medicines,* 



These aberrations in medical theory have their exact parallels in politics. 

 All the doctrines which ascribe absolute goodness to particular forms of 

 government, particular social arrangements, and even to particular modes of 

 education, without reference to the state of civilization and the various dis- 

 tinguishing characters of the society for which they ai'e intended, are open 

 to the same objection — that of assuming one class of influencing circum- 

 stances to be the paramount rulers of phenomena which depend in an equal 

 or greater degree on many others. But on these considerations it is the 

 less necessary that we should now dv/ell, as they will occupy our attention 

 more largely in the concluding Book. 



§ 6. The last of the modes of erroneous generalization to which I shall 

 advert, is that to which we may give the name of False Analogies. This 

 Fallacy stands distinguished from those already treated of by the peculiar- 

 ity that it does not even simulate a complete and conclusive induction, but 

 consists in the misapplication of an argument which is at best only admis- 

 sible as an inconclusive presumption, where real proof is unattainable. 



An argument fi'om analogy, is an inference that what is true in a certain 

 case is true in a case known to be somewhat similar, but not known to be 

 exactly parallel, that is, to be similar in all the material circumstances. An 

 object has the property B: another object is not known to have that prop- 

 erty, but resembles the first in a property A, not known to be connected 

 with B; and the conclusion to which the analogy points, is that this object 

 has the property B also. As, for example, that the planets are inhabited, 

 because the earth is so. The planets resemble the earth in describing 

 elliptical orbits round the sun, in being attracted by it and by one another, 

 in being nearly spherical, revolving on their axes, etc. ; and, as we have 

 now reason to believe from the revelations of the spectroscope, are com- 

 posed, in great part at least, of similar materials ; but it is not known that 

 any of these properties, or all of them together, are the conditions on Avhich 

 the possession of inhabitants is dependent, or are marks of those conditions. 

 Nevertheless, so long as we do not know what the conditions are, they 

 may be connected by some law of nature Avith those common properties; 

 and to the extent of that possibility the planets are more likely to be in- 

 habited than if they did not resemble tlie earth at all. This non-assignable 

 and generally small increase of probability, beyond what would otherwise 

 exist, is all the evidence which a conclusion can derive from analogy. For 

 if we have the slightest reason to suppose any real connection 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 a connection by causation between the fact of revolving on an axis 

 and the existence of animated beings, or if there were any reasonable 

 ground for even suspecting such a connection, a probability would arise 

 of the existence of inhabitants in the planets, which might be of any de- 

 gree 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 amounting to 



* Phannacologia, pp. 39, 40. 



