EXTENSION OF LAWS TO ADJACENT CASES. 85 



tained causes, from the laws of which the conjunction of their 

 effects is deducible. In that case, we may both extend the 

 derivative uniformity over a larger space, and with less abate 

 ment for the chance of counteracting causes. The first, 

 because instead of the local boundaries of our observation of 

 the fact itself, we may include the extreme boundaries of the 

 ascertained influence of its causes. Thus the succession of 

 day and night, we know, holds true of all the bodies of the 

 solar system except the sun itself; but we know this only 

 because we are acquainted with the causes : if we were not, 

 we could not extend the proposition beyond the orbits of the 

 earth and moon, at both extremities of which we have the 

 evidence of observation for its truth. With respect to the 

 probability of counteracting causes, it has been seen that this 

 calls for a greater abatement of confidence, in proportion to 

 our ignorance of the causes on which the phenomena depend. 

 On both accounts, therefore, a derivative law which we know 

 how to resolve, is susceptible of a greater extension to cases 

 adjacent in place, than a merely empirical law. 



