SENSATION. 13 



of its champions are those which are best described under 

 the head of a physiological law. 



THE LAW OF CONTRAST. 



I will first enumerate the main facts which fall under 

 this law, and then remark upon what seems to me their sig- 

 nificance for psychology.* 



[Nowhere are the phenomena of contrast better exhib- 

 ited, and their laws more open to accurate study, than in 

 connection with the sense of sight. Here both kinds — 

 simultaneous and successive — can easily be observed, for 

 they are of constant occurrence. Ordinarily they remain 

 unnoticed, in accordance with the general law of economy 

 which causes us to select for conscious notice only such 

 elements of our object as will serve us for aesthetic or prac- 

 tical utility, and to neglect the rest ; just as we ignore the 

 double images, the mouches volantes, etc., which exist for 

 everyone, but which are not discriminated without careful 

 attention. But by attention we may easily discover the 

 general facts involved in contrast. We find that in general 

 the color arid brightness of one object alivays apparently affect the 

 color and brightness of any other object seen simultaneously ivith 

 it or immediately after. 



In the first place, if we look for a moment at any surface 

 and then turn our eyes elsewhere, the complementary color 

 and opposite degree of brightness to that of the first surface 

 tend to mingle themselves with the color and the brightness 

 of the second. This is successive contrast. It finds its ex- 

 planation in the fatigue of the organ of sight, causing it to 

 respond to any particular stimulus less and less readily the 

 longer such stimulus continues to act. This is shown clearly 

 in the very marked changes which occur in case of contin- 

 ued fixation of one particular point of any field. The field 

 darkens slowly, becomes more and more indistinct, and 

 finally, if one is practised enough in holding the eye per- 



object as tlie latter is in itself. It has nothing to do with the question 

 which we have been discussing, of whether our objects of knowledge con- 

 tain absolute terms or consist altogether of relations. 



* What follows in brackets, as far as p. 27, is from the pen of my friend 

 and pupil Mr. E. B. Delabarre. 



