36 The Relativity of Knowledge. 



small quantity of tartaric acid in a large amount of water, 

 until it is just slightly sour. Let one gentleman swallow 

 some very sour solution slowly, and another one a very sweet 

 one. Now let both taste the dilute acid. No. 1 will de- 

 clare it positively sweet, and No. 2, annoyingly sour. The 

 thing itself is surely not both sweet and sour at the same 

 time. Put your right hand into hot Avater for a while, and 

 your left into cold. Now withdraw both and insert them 

 into a single pail containing te])id water. To the right 

 hand it will be cold, and to the left hot. Surely tluit water 

 is not both hot and cold at the same instant. Let two i)er- 

 sons stare, the one at a very red object and the other at a 

 bright green one ; then let them simultaneously look at a 

 light pink object. The man Avho stared at the green will be 

 sure it is bright red, and the man who stiired at the red 

 will be equally sure it is bright green. (Illustrated on the 

 screen, by the stereopticon.) Is it both red and green at 

 the same time ? 



The fact revealed by all these experiments is that sensa- 

 tions are states of the conscious-being, and that we have 

 no reason for assuming that things in themselves are like 

 the sensations they produce. Changes in the individual 

 produce changes in the sensations, though we are morally 

 certain that no corresponding change occurs in the external 

 things themselves. Every one has observed how differ- 

 ently his taste has been affected by the same articles of 

 food when sick and when well. So decided, indeed, does 

 this difference become, that things at one time desired, at 

 another become positively obnoxious. There is no change in 

 the food. The change is in the patient. Then, on the 

 other hand, tobacco, at first decidedly disgusting, comes at 

 last to be craved as a sweet morsel. If taste was an actiud 

 quality existing in the things, no change of the individual 

 could alter it. AVe do know Avith certainty how things 

 affect lis, but when Ave assert that this effect is like that 

 Avhich caused it Ave go farther than sound reasoning can 

 tolerate. 



While thus subject to fluctuations, there is a sort of ])ar- 

 allelism between sensations and the things Avliich induce 

 them. Sugar Avhen out of the mouth, though free from 

 sweetness, does possess some property that in the mouth 

 produces SAveetness. A cannon, fired Avhere there are no 

 ears, may evoke no sound ; but there is something produced 



