FALLACIES OF GENERALIZATION. 409 



important addition to our knowledge if proved, that 

 certain motions in the particles of bodies are among 

 the conditions of the production of heat or light; that 

 certain assignable physical modifications of the nerves 

 may be among the conditions not only of our sensa- 

 tions or emotions, but even of our thoughts; that 

 certain mechanical and chemical conditions may, in 

 the order of nature, be sufficient to determine to 

 action the physiological laws of life. All I insist 

 upon, in common with every sober thinker since 

 modern science has been definitively constituted, is, 

 that it shall not be supposed that by proving these 

 things one step would be made towards a real expla- 

 nation of heat, light, or sensation ; or that the generic 

 peculiarity of those phenomena can be in the least 

 degree evaded by any such discoveries, however well 

 established. Let it be shown, for instance, that the 

 most complex series of physical causes and effects 

 succeed one another in the eye and in the brain to 

 produce a sensation of colour ; rays falling upon 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 nervous 

 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 mo- 

 tions as you choose; still, at the end of these motions, 

 there is something which is not a motion, there is a 

 feeling or sensation of colour. Whatever number 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 motion antecedent and a colour 

 consequent. The mode in which any one of the 

 motions produces the next, might possibly be suscep- 

 tible of explanation by some general law of motion 



