134 FRAGMENTS OF SCIENCE. 



which the world of sense itself is the suggestion and justi- 

 fication. 



Far be it from me, however, to wish to fix you immov- 

 ably in this or in any other theoretic conception. With 

 all our belief of it, it will be well to keep the theory plastic 

 and capable of change. You may, moreover, urge that 

 although the phenomena occur as if the medium existed, 

 the absolute demonstration of its existence is still wanting. 

 Far be it from me to deny to this reasoning such validity 

 as it may fairly claim. Let us endeavor by means of anal- 

 ogy to form a fair estimate of its force. You believe that 

 in society you are surrounded by reasonable beings like 

 yourself. You are perhaps as firmly convinced of this as 

 of any thing. What is your warrant for this conviction ? 

 Simply and solely this, your fellow-creatures behave as if 

 they were reasonable ; the hypothesis, for it is nothing 

 more, accounts for the facts. To take an eminent example : 

 you believe that our President is a reasonable being. Why ? 

 There is no known method of superposition by which any 

 one of us can apply himself intellectually to another so as 

 to demonstrate coincidence as regards the possession of 

 reason. If, therefore, you hold our President to be reason- 

 able, it is because he behaves as if he were reasonable. As 

 in the case of the ether, beyond the " as if" you cannot go. 

 Nay I should not wonder if a close comparison of the data 

 on which both inferences rest, caused many respectable 

 persons to conclude that the ether had the best of it. 



This universal medium, this light-ether as it is called, is 

 a vehicle, not an origin of wave-motion. It receives and 

 transmits, but it does not create. Whence does it derive 

 the motions it conveys ? For the most part from luminous 

 bodies. By this motion of a luminous body I do not mean 

 its sensible motion, such as the flicker of a candle, or the 

 shooting out of red prominences from the limb of the sun. 

 I mean an intestine motion of the atoms or molecules of 



