EXPLANATION OF LAWS. 549 



contribute to it. Thus, the law of the motion of a 

 planet is resolved into the law of the tangential force, 

 which tends to produce an uniform motion in the 

 tangent, and the law of the centripetal force, which 

 tends to produce an accelerating motion towards 

 the sun ; the real motion being a compound of the 

 two. 



It is necessary here to remark, that in this resolu- 

 tion of the law of a complex effect, the laws of which 

 it is compounded are not the only elements. It is 

 resolved into the laws of the separate causes, together 

 with the fact of their coexistence. The one is as 

 essential an ingredient as the other; whether the 

 object be to discover the law of the effect, or only to 

 explain it. To deduce the laws of the heavenly 

 motions, we require not only to know the law of a 

 rectilineal and that of a gravitative force, but the 

 existence of both these forces in the celestial regions, 

 and even their relative amount. The complex laws 

 of causation are thus resolved into two distinct kinds 

 of elements : the one, simpler laws of causation, the 

 other (in the aptly selected language of Dr. Chalmers) 

 collocations ; the collocations consisting in the exist- 

 ence of certain agents or powers, in certain circum- 

 stances of place and time. We shall hereafter have 

 occasion to return to this distinction, and to dwell 

 upon it at such a length as dispenses with the neces- 

 sity of further insisting upon it here. The first mode, 

 then, of the explanation of Laws of Causation, is when 

 the law of an effect is resolved into the various ten- 

 dencies of which it is the result, and into the laws of 

 those tendencies. 



3. A second case is when, between what seemed 

 the cause and what was supposed to be its effect, 



