548 FALLACIES. 



law of causality itself. That no variation in any effect or consequent will 

 take place while the whole of the antecedents remain the same, may be 

 affirmed with full assurance. But, that the addition of some new anteced- 

 ent might not entirely alter and subvert the accustomed 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 generalizations which profess, 

 like the theories of Thales, Democritus, and others of the early Greek 

 speculators, to resolve all things into some one element, or like many mod- 

 ern theories, to resolve phenomena radically different into the same, ai-e 

 necessarily false. By radically different phenomena I mean impressions 

 on our senses which differ in quality, and not merely in degree. On this 

 subject what appeared necessary was said in the chapter on the Limits to 

 the Explanation of Laws of Nature ; but as the fallacy is even in our own 

 times a common one, I shall touch on it somewhat further in this place. 



When we say that the force which retains the planets in their orbits is 

 resolved into gravity, or that the force which makes substances combine 

 chemically is resolved into electricity, we assert in the one case what is, 

 and in the other case wliat might, and probably will ultimately, be a legiti- 

 mate result of induction. In both these cases motion is resolved into mo- 

 tion. 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 another class of motions. But, from 

 these and similar generalizations, countenance 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 phi- 

 losophy; 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 assignable physical modifications of the nerves 

 may be the conditions not only of our sensations or emotions, but even of 

 our thoughts; that certain mechanical and chemical conditions may, in the 

 order of nature, be sufficient to detei'mine to action the physiological 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 made toward a real explanation 

 of heat, light, or sensation ; or that the generic peculiarity of those phe- 

 nomena can be in the least degree evaded by any such discoveries, how- 

 ever well established. Let it be shown, for instance, that the most com- 

 plex series of physical causes and effects succeed one another in the eye 

 and in the brain to produce a sensation of color ; rays falling on the eye, 

 refracted, converging, crossing one another, making an inverted image on 

 the retina, and after this a motion — let it be a vibration, or a rush of nerv- 

 ous fluid, or whatever else you are pleased to suppose, along the optic 

 nerve — a propagation of this motion to the brain itself, and as many more 

 different motions as you choose ; still, at the end of these motions, there is 

 something which is not motion, there is a feeling or sensation of color. 

 Whatever immber of motions we may be able to interpolate, and whether 

 they be real or imaginary, we shall still find, at the end of the series, a rao- 



