tJXAMPLES OF TSl! l5Xt*LANATI0N OF LAWS. 



311 



tendency of all particles of matter to- 

 wards one another. It must be kept 

 constantly in view, therefore, that in 

 science, those who speak of explain- 

 ing any phenomenon mean (or should 

 mean) pointing out not some more 

 familiar, but merely some more gene- 

 ral phenomenon, of which it is a par- 

 tial exemplification ; or some laws of 

 causation which produce it by their 

 joint or successive action, and from 

 which, therefore, its conditions may 

 be determined deductively. Every 

 such operation brings us a step nearer 

 towards answering the question which 

 was stated in a previous chapter as 

 comprehending the whole problem of 

 the investigation of nature, viz. What 

 are the fewest assumptions, which 

 being granted, the order of nature as 

 it exists would be the result ? What 

 are the fewest general propositions 

 from which all the uniformities exist- 

 ing in nature could be deduced ? 



The laws, thus explained or re- 

 solved, are sometimes said to be ac- 

 counted for ; but the expression is 

 incorrect, if taken to mean anything 

 more than what has been already 

 stated. In minds not habituated to 

 accurate thinking, there is often a 

 confused notion that the general laws 

 are the causes of the partial ones ; 

 that the law of general gravitation, 

 for example, causes the phenomenon 

 of the fall of bodies to the earth. But 

 to assert this would be a misuse of 

 the word cause : terrestrial gravity is 

 not an effect of general gravitation, 

 but a case of it ; that is, one kind of 

 the particular instances in which that 

 general law obtains. To account for 

 a law of nature means, and can mean, 

 nothing more than to assign other 

 laws more general, together with col- 

 locations, which laws and collocations 

 being supposed, the partial law fol- 

 lows without any additional supposi- 

 tion. 



CHAPTER XIII. 



MISCELLANEOUS EXAMPLES OF TH« EX- 

 PLANATION OF LAWS OF NATURE. 



§ I. The most striking example 

 which the history of science presents 

 of the explanation of laws of causa- 

 tion and other uniformities of sequence 

 among special phenomena, by resolv- 

 ing them into laws of greater sim- 

 plicity and generality, is the great 

 Newtonian generalisation : respecting 

 which typical instance so much having 

 already been said, it is sufficient to 

 call attention to the great number 

 and variety of the special observed 

 uniformities which are in this case 

 accounted for, either as particular 

 cases, or as consequences of one very 

 simple law of universal nature. The 

 simple fact of a tendency of every 

 particle of matter towards every other 

 particle, varying inversely as the 

 square of the distance, explains the 

 fall of bodies to the earth, the revolu- 

 tions of the planets and satellites, the 

 motions (so far as known) of comets, 

 and all the various regularities which 

 have been observed in these special 

 phenomena ; such as the elliptical 

 orbits, and the variations from exact 

 ellipses ; the relation between the 

 solar distances of the planets and the 

 duration of their revolutions ; the 

 precession of the equinoxes ; the 

 tides, and a vast number of minor 

 astronomical truths. 



Mention has also been made in the 

 preceding chapter of the explanation 

 of the phenomena of magnetism from 

 laws of electricity ; the special laws 

 of magnetic agency having been aflfi- 

 liated by deduction to observed laws 

 of electric action, in which they have 

 ever since been considered to be in- 

 cluded as special cases. An example 

 not so complete in itself, but even 

 more fertile in consequences, having 

 been the starting-point of the really 

 scientific study of physiology, is the 

 affiliation, commenced by Bichat, and 

 carried on by subsequent biologists, 

 of the properties of the bodily organs 



