414 INDUCTION. 



all concerned in the matter, argues a combination of many causes, and 

 therefore a great liability to counteraction ; while the comparatively nar- 

 row range of the observations renders it impossible to predict to what ex- 

 tent unknown counteracting causes may be distributed throughout nature. 

 But when a generalization has been found to hold good of a very large 

 proportion of all things whatever, it is already proved that nearly all the 

 causes which exist in nature have no power over it ; that very few changes 

 in the combination of causes can affect it ; since the greater number of 

 possible combinations must have already existed in some one or other of 

 the instances in which it has been found true. If, therefore, any empirical 

 law is a I'esult of causation, the more general it is, the more it may be de- 

 pended on. And even if it be no result of causation, but an ultimate co- 

 existence, the more general it is, the greater amount of experience it is de- 

 rived from, and the greater therefore is the probability that if exceptions 

 had existed, some would already have presented themselves. 



For these reasons, it requires much more evidence to establish an excep- 

 tion to one of the more general empirical laws than to the more special 

 ones. We should not have any difficulty in believing that there might be 

 a new Kind of crow ; or a new kind of bird resembling a crow in the 

 properties hitherto considered distinctive of that Kind. But it would re- 

 quire stronger proof to convince us of the existence of a Kind of crow hav- 

 ing properties at variance with any generally recognized universal property 

 of birds ; and a still higher degree if the properties conflict with any rec- 

 ognized universal property of animals. And this is conformable to the 

 mode of judgment recommended by the common sense and general prac- 

 tice of mankind, who are more incredulous as to any novelties in natui'e, 

 according to the degree of generality of the experience which these novel- 

 ties seem to contradict. 



§ 9. It is conceivable that the alleged properties might conflict with 

 some recognized universal property of all matter. In that case their im- 

 probability would be at the highest, but would not even then amount to 

 incredibility. There are only two known properties common to all mat- 

 ter ; in other words, there is but one known uniformity of co-existence of 

 properties co-extensive with all physical nature, n.imely, that whatever op- 

 poses resistance to movement gravitates, or, as Professor Bain expresses it, 

 Inertia and Gravity are co-existent through all matter, and proportionate 

 in their amount. These properties, as he truly says, are not mutually im- 

 plicated ; from neither of them could we, on grounds of causation, presume 

 the other. But, for this very reason, we are never certain that a Kind may 

 not be discovered possessing one of the properties without the other. The 

 hypothetical ether, if it exists, may be such a Kind. Our senses can not 

 recognize in it either resistance or gravity ; but if the reality of a resisting 

 medium should eventually be proved (by alteration, for example, in the 

 times of revolution of periodic comets, combined with the evidences afford- 

 ed by the phenomena of light and heat), it would be rash to conclude from 

 this alone, without other proofs, that it must gravitate. 



For even the greater generalizations, which embrace comprehensive Kinds 

 containing under them a great number and variety of infimce species, are 

 only empirical laws, resting on induction by simple enumeration merely, and 

 not on any process of elimination — a process wholly inapplicable to this 

 sort of case. Such generalizations, therefore, ought to be grounded on an 

 examination of all the inJimcB species comprehended in them, and not of a 



