COEXISTENCES INDEPENDENT OF CAUSATION. 119 



none of their properties are ultimate, but all of them deriva- 

 tive, and produced by causation. And the presumption is 

 confirmed, by the fact that the properties which vary from 

 one individual to another, also generally vary more or less at 

 different times in the same individual ; which variation, like 

 any other event, supposes a cause, and implies, consequently, 

 that the properties are not independent of causation. 



If, therefore, blackness be merely accidental in crows, 

 and capable of varying while the Kind remains the same, its 

 presence or absence is doubtless no ultimate fact, but the 

 effect of some unknown cause : and in that case the univer- 

 sality 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 every- 

 where 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 discovered, 

 should exist in nature, is a supposition so often realized, that 

 it cannot be considered at all improbable. We have nothing 

 to authorize us in attempting 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 explored ; 

 and even this improbability depends on the degree of con- 

 spicuousness 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 



