CO EXISTENCES INDEPENDENT OF CAUSATION. 413 



varying while the Kind remains the same, its presence or absence is doubt- 

 less no ultimate fact, but the effect of some unknown cause : and in that 

 case the universality of the experience that all crows are black is sufficient 

 proof of a common cause, and establishes the generalization as an empirical 

 law. Since there are innumerable instances in the affirmative, and hitherto 

 none at all in the negative, the causes on which the property depends must 

 exist everywhere in the limits of the observations which have been made ; 

 and the proposition may be received as universal within those limits, and 

 with the allowable degree of extension to adjacent cases. 



§ 7. If, in the second place, the property, in the instances in which it has 

 been observed, is not an effect of causation, it is a property of Kind ; and 

 in that case the generalization can only be set aside by the discovery of a 

 new Kind of crow. That, however, a peculiar Kind not hitherto discover- 

 ed should exist in nature, is a supposition so often realized that it can not 

 be considered at all improbable. We have nothing to authorize us in at- 

 tempting to limit the Kinds of things which exist in nature. The only 

 unlikelihood would be that a new Kind should be discovered in localities 

 which there was previously reason to believe had been thoroughly ex- 

 plored ; and even this improbability depends on the degree of conspicuous- 

 ness of the difference between the newly-discovered Kind and all others, 

 since new kinds of minerals, plants, and even animals, previously overlooked 

 or confounded with known species, are still continually detected in the 

 most frequented situations. On this second ground, therefore, as well as 

 on the first, the observed uniformity of co-existence can only hold good as 

 an empirical law, within the limits not only of actual observation, but of an 

 observation as accurate as the nature of the case required. And hence it 

 is that (as remarked in an early chapter of the present book) we so often 

 give up generalizations of this class at the first summons. If any credible 

 witness stated that he had seen a white crow, under circumstances which 

 made it not incredible that it should have escaped notice previously, we 

 should give full ci'edence to the statement. 



It appears, then, that the uniformities which obtain in the co-existence of 

 phenomena — those which we have reason to consider as ultimate, no less 

 than those which arise from the laws of causes yet undetected — are entitled 

 to reception only as empirical laws ; are not to be presumed true except 

 within the limits of time, place, and circumstance, in which the observa- 

 tions were made, or except in cases strictly adjacent. 



§ 8. We have seen in the last chapter that there is a point of generality 

 at which empirical laws become as certain as laws of nature, or, rather, at 

 which there is no longer any distinction between empirical laws and laws 

 of nature. As empirical laws approach this point, in other words, as they 

 rise in their degree of generality, they become more certain ; their univer- 

 sality may be more strongly relied on. For, in the first place, if they are 

 results of causation (which, even in the class of uniformities treated of in 

 the present chapter, we never can be certain that they are not) the more 

 general they are, the greater is proved to be the space over which the 

 necessary collocations prevail, and within which no causes exist capable of 

 counteracting the unknown causes on which the empirical law depends. 

 To say that any thing is an invariable property of some very limited class 

 of objects, is to say that it invariably accompanies some very numerous 

 and complex group of distinguishing properties j which, if causation be at 



