FALLACIES OF GENERALISATION. 



51S 



ters dependent on causation, are all 

 * universal negatives, all propositions 

 that assert impossibility. The non- 

 existence of any given phenomenon, 

 however uniformly experience may as 

 yet have testified to the fact, proves 

 at most that no cause adequate to its 

 production has yet manifested itself ; 

 but that no such causes exist in nature 

 can only be inferred if we are so fotJ- 

 ish as to suppose that we know all 

 the forces in nature. The supposition 

 would at least be premature while our 

 acquaintance with some, even of those 

 which we do know, is so extremely re- 

 cent. And, however much our know- 

 ledge of nature may hereafter be ex- 

 tended, it is not easy to see how that 

 knowledge could ever be complete, or 

 how, if it were, we could ever be as- 

 sured of its being so. 



The only laws of nature which afford 

 sufficient warrant for attributing im- 

 possibility (even with reference to the 

 existing order of nature, and to our 

 own region of the universe) are, first, 

 those of number and extension, which 

 are paramount to the laws of the suc- 

 cession of phenomena, and not exposed 

 to the agency of counteracting causes ; 

 and, secondly, the universal law of 

 causality itself. That no variation in 

 any effect or consequent will take place 

 while the whole of the antecedents re- 

 main the same, may be affirmed with 

 full assurance. But that the addition 

 of some new antecedent might not 

 entirely alter and subvert the accus- 

 tomed consequent, or that antecedents 

 competent to do this do not exist in 

 nature, we are in no case empowered 

 positively to conclude. 



§ 3. It is next to be remarked that 

 all generalisations which pi-ofess, like 

 the theories of Thales, Democritus, 

 and others of the early Greek specula- 

 tors, to resolve all things into some one 

 element, or, like many modern theories, 

 to resolve phenomena radically differ- 

 ent into the same, are necessarily false. 

 By radically different phenomena T 

 mean impressions on our senses which 

 differ in quality, and not merely in de- 



gree. On this subject what appeared 

 necessary was said in the chapter on 

 the Limits to the Explanation of Laws 

 of Nature ; but as tlie fallacy is even 

 in our own times a common one, I 

 shall touch on it somewhat further ia 

 this place. 



When we gay that the force which 

 retains the planets in their orbits is 

 resolved into gravity, or that tlie 

 force which makes substances combine 

 chemically is resolved into electricity, 

 we assert in the one case what is, and 

 in the other case what might, and 

 probably will ultimately, be a legiti- 

 mate result of induction. In both 

 these cases motion is resolved into 

 motion. The assertion is, that a case 

 of motion, which was supposed to be 

 special and to follow a distinct law of 

 its own, conforms to and is included in 

 the general law which regulates an- 

 other class of motions. But, from these 

 and similar generalisations, counten- 

 ance and currency have been given to 

 attempts to resolve, not motion into 

 motion, but heat into motion, light into 

 motion, sensation itself into motion ; 

 states of consciousness into states of 

 the nervous system, as in the ruder 

 forms of the Materialist philosophy ; 

 vital phenomena into mechanical or 

 chemical processes, as in some schools 

 of physiology. 



Now I am far from pretending that 

 it may not be capable of proof, or that 

 it is not an important addition to 

 our knowledge if proved, that cer- 

 tain motions in the particles of bodies 

 are the conditions of the production 

 of heat or light ; that certain assign- 

 able physical modifications of the 

 nerves may be the conditions not only 

 of our sensations and emotions, but 

 even of our thoughts ; that certain 

 mechanical and chemical conditions 

 may, in the order of nature, be suf- 

 ficient to determine to action the phy- 

 siological laws of life. All, I insist 

 upon, in common with every thinker 

 who entertains any clear idea of the 

 logic of science, is that it shall not be 

 supposed that by proving these things 

 one step would be niade towards fv re^J 



