NECESSARY TRUTHS— EFFECTS OF EXPERIENCE. 667 



gases, etc., etc., begins by saying that the only facts are 

 collocations and motions of primordial solids, and the only 

 laws the changes of motion which changes in collocation 

 bring. The ideal which this jDhilosophy strives after is a 

 mathematical world-formula, by which, if all the colloca- 

 tions and motions at a given moment were known, it would 

 be possible to reckon those of any wished-for future mo- 

 ment, by simply considering the necessarj^ geometrical, 

 arithmetical, and logical implications. Once we have the 

 world in this bare shape, we can fling our net of a priori 

 relations over all its terms, and pass from one of its phases 

 to another by inward thought-necessity. Of course it is a 

 world with a very minimum of rational sinff. The senti- 

 mental facts and relations are butchered at a blow. But 

 the rationality yielded is so superbly complete in form that 

 to many minds this atones for the loss, and reconciles the 

 thinker to the notion of a purposeless universe, in which 

 all the things and qualities men love, dulcissiina mundi 

 nomina, are but illusions of our fancy attached to accidental 

 clouds of dust which will be dissipated by the eternal 

 cosmic weather as carelessly as they were formed. 



The popular notion that ' Science ' is forced on the mind 

 ah extra, and that our interests have nothing to do with its 

 constructions, is utterl}^ absurd. The craving to believe 

 that the things of the world belong to kinds which are rela- 

 ted by inward rationality together, is the parent of Science 

 as well as of sentimental philosophy ; and the original in- 

 vestigator always preserves a healthy sense of how jilastic 

 the materials are in his hands. 



" Once for all," says Helmboltz in beginning that little work of his 

 which laid the foundations of the 'conservation of energy,' "it is the 

 task of the physical sciences to seek for laws by which particular pro- 

 cesses in nature may be referred to general rules, and deduced from 

 such again. Such rules (for example the laws of reflection or refrac- 

 tion of light, or that of Mariotte and Gay-Lussac for gas-volumes) are 

 evidently nothing but generic-concepts for embracing whole classes of 

 phenomena. The search for them is the business of the experimental 

 division of our Science. Its theoretic division, on the other hand, 

 tries to discover the unknown causes of processes from their visible 

 effects ; tries to understand them by the law of causality. . . . The 

 ultimate goal of theoretic physics is to find the last unchanging causes 



