ftMPtRICAL LAWS. 



345 



cefesefi. Nutrition is the addition of 

 particles to one another, sometimes 

 merely replacing other particles sepa- 

 rated and excreted, sometimes oc- 

 casioning an increase of bulk or 

 weight so gradual, that only after 

 a long continuance does it become per- 

 ceptible. Various organs, by means 

 of peculiar vessels, secrete from the 

 blood fluids, the component particles 

 of which must have been in the blood, 

 but which differ from it most widely 

 both in mechanical properties and in 

 chemical composition. Here, then, 

 aie abundance of unknown links to 

 be filled up ; and there can be no 

 doubt that the laws of the pheno- 

 mena of vegetative or organic life are 

 derivative laws, dependent on pro- 

 perties of the corpuscles, and of those 

 elementary tissues which are com- 

 paratively simple combinations of cor- 

 puscles. 



The first sign, then, from which a 

 law of causation, though hitherto im- 

 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 com- 

 plex phenomenon, and its effects 

 therefore, probably in part at least, 

 compounded of the effects of its dif- 

 ferent 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 Com- 

 position of Causes being by far the 

 more ordinary case. 



We will illustrate this by two ex- 

 amples, in one of which the antece- 

 dent 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 gravi- 

 tate to one another in proportion to 

 their quantity of matter. All true 

 propositions, therefore, which can be 

 made concerning gravity are deri- 

 vative laws : the ultimate law into 



which they are all resolvable being 

 that every particle of matter attracts 

 every other. As our second example, 

 we may take any of the sequence* 

 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 pheno- 

 menon, made up of heterogeneous 

 elements ; the column of the atmos- 

 phere over any particular place con- 

 sisting of two parts, a column of air 

 and a column of aqueous vapour 

 mixed with it ; and the change in the 

 two together manifested by a fall of 

 the barometer, and followed 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 reason- 

 able presumption, from the invariable 

 presence of both these elements in the 

 antecedent, that the sequence is pro- 

 bably not an ultimate law, but a re- 

 sult of the laws of the two different 

 agents ; a presumption only to be de- 

 stroyed 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 themselves produce 

 the observed result. 



There are but few known cases of 

 succession from very complex ante- 

 cedents which have not either been 

 actually accounted for from simpler 

 laws, or inferred with great proba- 

 jility (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 lawis of organised nature are re- 

 solvable into simpler laws, it would 

 be almost a sufficient reason that the 

 antecedents in most of the sequence* 

 are so very complex. 



§ 7. In the preceding discussion we 



