HYPOTHESES. 



3'^ 



lehich are distinguishable from one 

 another in quality, and not merely in 

 quantity or degree. For example, 

 since there is a phenomenon sui gene- 

 ris called colour, which our conscious- 

 ness testifies to be not a particular 

 degree of some other phenomenon, as 

 heat, or odour, or motion, but intrin- 

 sically unlike all others, it follows 

 that there are ultimate laws of colour ; 

 that though the facts of colour may 

 admit of explanation, they never can 

 be explained from laws of heat or 

 odour alone, or of motion alone, but 

 that, however far the explanation 

 may be carried, there will always re- 

 main in it a law of colour. I do not 

 mean that it might not possibly be 

 shown that some other phenomenon, 

 some chemical or mechanical ac- 

 tion, for example, invariably precedes 

 and is the cause of every phenome- 

 non of colour. But though this, if 

 proved, would be an important ex- 

 tension of our knowledge of nature, 

 it would not explain how or why 

 a motion or a chemical action can 

 produce a sensation of colour ; and 

 however diligent might be our scru- 

 tiny of the phenomena, whatever 

 number of hidden links we might de- 

 tect in the chain of causation termi- 

 nating in the colour, the last link 

 would still be a law of colour, not a 

 law of motion, nor of any other phe- 

 nomenon whatever. Nor does this 

 observation apply only to colour, as 

 compared with any other of the great 

 classes of sensations ; it applies to 

 every particular colour, as compared 

 with others. White colour can in no 

 manner be explained exclusively by 

 the laws of the production of red 

 colour. In any attempt to explain 

 it, we cannot but introduce, as one 

 element of the explanation, the pro- 

 position that some antecedent or other 

 produces the sensation of white. 



The ideal limit, therefore, of the 

 explanation of natural phenomena 

 (towards which, as towards other ideal 

 limits, we are constantly tending, 

 without the prospect of ever com- 

 pletely attaining it) would be to show 



that each distinguishable variety of 

 our sensations, or other states of con- 

 sciousness, has only one sort of cause : 

 that, for example, whenever we per- 

 ceive a white colour, there is som© 

 one condition or set of conditions 

 which is. always present, and the 

 presence of which always produces in 

 us that sensation. As long as there 

 are several known modes of produc- 

 tion of a phenomenon, (several dif- 

 ferent substances, for instance, which 

 have the property of whiteness, and 

 between which we cannot trace any 

 other resemblance,) so long it is not 

 impossible that one of these modes 

 of production may be resolved into 

 another, or that all of them may be 

 resolved into some more general mode 

 of production not hitherto recognised. 

 But when the modes of production 

 are reduced to one, we cannot, in 

 point of simplification, go any further. 

 This one may not, after all, be the 

 ultimate mode ; there may be other 

 links to be discovered between the 

 supposed cause and the effect ; but 

 we can only further resolve the known 

 law, by introducing some other law 

 hitherto unknown ; which will not 

 diminish the number of ultimate 

 laws. 



In what cases, accordingly, has 

 science been most successful in ex- 

 plaining phenomena, by resolving 

 their complex laws into laws of greater 

 simplicity and generality ? Hitherto 

 chiefly in cases of the propagation of 

 various phenomena through space : 

 and, first and principally, the most 

 extensive and important of all facts of 

 that description, mechanical motion. 

 Now this is exactly what might be 

 expected from the principles here laid 

 down. Not only is motion one of 

 the most universal of all phenomena, 

 it is also (as might be expected from 

 that circumstance) one of those which, 

 apparently at least, are produced in 

 the greatest number of ways ; but the 

 phenomenon itself is always, to our 

 sensations, the same in every respect 

 but degree. Differences of duration 

 or of velocity are evidently differ- 



