CO-EXISTENCES INDEPENDENT OF CAUSATION. 



flict with any recognised universal 

 property of animals. And this is 

 conformable to the mode of judgment 

 recommended by the common sense 

 and general practice of mankind, who 

 are more incredulous as to any novel- 

 ties in nature, according to the degree 

 of generality of the experience which 

 these novelties seem to contradict. 



§ 9. It is conceivable that the al- 

 leged properties might conflict with 

 some recognised universal property of 

 all matter. In that case their impro- 

 bability would be at the highest, but 

 would not even then amount to in- 

 credibility. There are only two known 

 properties common to all matter ; in 

 other words, there is but one known 

 uniformity of co-existence of proper- 

 ties, co-extensive with all physical 

 nature, namely, that whatever op- 

 poses resistance to movement, gravi- 

 tates ; 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 cannot 

 recognise in it either resistance or 

 gravity ; but if the reality of a resist- 

 ing medium should eventually be 

 proved, (by alteration, for example, in 

 the times of revolution of periodic 

 comets, combined with the evidences 

 afforded by the phenomena of light 

 and heat,) it would be rash to con- 

 clude from this alone, without other 

 proofs, that it must gravitate. 



For even the greater generalisa- 

 tions which embrace comprehensive 

 Kinds containing under them a great 

 number and variety of injimce species, 

 are only empirical laws, resting on 

 induction by simple enumeration 

 merely, and not on any process of 

 elimination, a process wholly inappli- 



cable to this sort of case. Such gene- 

 ralisations, therefore, ought to be 

 grounded on an examination of all 

 the injimce species comprehended in 

 them, and not of a portion only. We 

 cannot conclude (where causation is 

 not concerned) because a proposition 

 is true of a number of things resem- 

 bling one another only in being ani- 

 mals, that it is therefore true of all 

 animals. If, indeed, anything be 

 true of species which differ more from 

 one another than either differs from 

 a third, (especially if that third spe- 

 cies occupies in most of its known 

 properties a position between the two 

 former,) there is some probability that 

 the same thing will also be true of 

 that intermediate species ; for it is 

 often, though by no means universally 

 found, that there is a sort of paral- 

 lelism in the properties of different 

 Kinds, and that their degree of unlike- 

 ness in one respect bears some propor- 

 tion to their unlikeness in others. We 

 see this parallelism in the properties of 

 the different metals ; in those of sul- 

 phur, phosphorus, and carbon ; of chlo- 

 rine, iodine, and bromine , in the natu- 

 ral orders of plants and animals, &c. 

 But there are innumerable anomalies 

 and exceptions to this sort of confor- 

 mity ; if indeed the conformity itself 

 be anything but an anomaly and an 

 exception in nature. 



Universal propositions, therefore, 

 respecting the properties of superior 

 Kinds, unless grounded on proved or 

 presumed connection by causation, 

 ought not to be hazarded except after 

 separately examining every known 

 sub-kind included in the larger Kind. 

 And even then such generalisations 

 must be held in readiness to be given 

 up on the occurrence of some new 

 anomaly, which, when the uniformity 

 is not derived from causation, can 

 never, even in the case of the most 

 general of these empirical laws, be 

 considered very improbable. Thus 

 all the universal propositions which 

 it has been attempted to lay down 

 respecting simple substances, or con- 

 cerning any of the classes which have 

 2 B 



