EMPIRICAL LAWS. 371 



The first sign, then, from which a law of causation, though hitherto un- 

 resolved, may be inferred to be a derivative law, is any indication of the 

 existence of an intermediate link or links between the antecedent and the 

 consequent. The second is, when the antecedent is an extremely complex 

 phenotnenon, and its effects, therefore, probably in part at least, compound- 

 ed of the effects of its different elements ; since we know that the case in 

 which the effect of the whole is not made up of the effects of its parts is 

 exceptional, the Composition of Causes being by far the more ordinary 

 case. 



We will illustrate this by two examples, in one of which the antecedent is 

 the sum of many homogeneous, in the other of heterogeneous, parts. The 

 weight of a body is made up of the weights of its minute particles ; a truth 

 which astronomers express in its most general terms when they say that 

 bodies, at equal distances, gi-avitate to one another in proportion to their 

 quantity of matter. All true propositions, therefore, which can be made 

 concerning gravity, are derivative laws ; the ultimate law into which they 

 are all resolvable being, that eveiy particle of matter attracts every other. 

 As our second example, we may take any of the sequences observed in 

 meteorology ; for instance, a diminution of the pressure of the atmosphere 

 (indicated by a fall of the barometer) is followed by rain. The antecedent 

 is here a complex phenomenon, made up of heterogeneous elements ; the 

 column of the atmosphere over any particular place consisting of two parts, 

 a column of air, and a column of aqueous vapor mixed with it; and the 

 change in the two together manifested by a fall of the barometer, and fol- 

 lowed by rain, must be either a change in one of these, or in the other, or 

 in both. We might, then, even in the absence of any other evidence, form 

 a reasonable presumption, from the invariable presence of both these ele- 

 ments in the antecedent, that the sequence is probably not an ultimate law, 

 but a result of the laws of the two different agents; a presumption only 

 to be destroyed when we had made ourselves so well acquainted with the 

 laws of both, as to be able to affirm that those laws could not by them- 

 selves produce the observed result. 



There are but few known cases of succession from veiy complex ante- 

 cedents which have not either been actually accounted for from simpler 

 laws, or inferred with great probability (from the ascertained existence of 

 intermediate links of causation not yet understood) to be capable of being 

 so accounted for. It is, therefore, highly probable that all sequences from 

 complex antecedents are thus resolvable, and that ultimate laws are in all 

 cases comparatively simple. If there were not the other reasons already 

 mentioned for believing that the laws of organized nature are resolvable 

 into simpler laws, it would be almost a sufficient reason that the ante- 

 cedents in most of the sequences are so very complex. 



§ 7. In the pi'eceding discussion we have recognized two kinds of em- 

 piiical laws : those known to be laws of causation, but presumed to be re- 

 solvable into simpler laws ; and those not known to be laws of causation 

 at all. Both these kinds of laws agree in the demand which they make for 

 being explained by deduction, and agree in being the appropriate means 

 of verifying such deduction, since they represent the experience with which 

 the result of the deduction must be compared. They agree, further, in 

 this, that until explained, and connected with the ultimate laws from which 

 they result, they have not attained the highest degree of certainty of which 

 laws ai-e susceptible. It has been shown on a former occasion that laws 



