SCIENTIFIC USE OF THE IMAGINATION. 1Q7 



and, endowing it with one or two other necessary 

 qualities, let us handle it in accordance with strict 

 mechanical laws. Let us then carry our results from 

 the world of theory into the world of sense, and see 

 whether our deductions do not issue in the very phe- 

 nomena of light which ordinary knowledge and skilled 

 experiment reveal. If in all the multiplied varieties 

 of these phenomena, including those of the most re- 

 mote and entangled description, this fundamental 

 conception always brings us face to face with the 

 truth; if no contradiction to our deductions from it 

 be found in external nature, but on all sides agree- 

 ment and verification; if, moreover, as in the case of 

 Conical Refraction and in other cases, it actually forces 

 upon our attention phenomena which no eye had pre- 

 viously seen, and which no mind had previously im- 

 agined such a conception, must, we think, be some- 

 thing more than a mere figment of the scientific fancy. 

 In forming it, that composite and creative power, in 

 which reason and imagination are united, has, we be- 

 lieve, led us into a world not less real than that of the 

 senses, and of which the world of sense itself is the sug- 

 gestion and, to a great extent, the outcome. 



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

 immovably in this or in any other theoretic conception. 

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

 theory of a luminiferous ether plastic and capable of 

 change. You may, moreover, urge that, although the 

 phenomena occur as if the medium existed, the ab- 

 solute demonstration of its existence is still wanting. 

 Far be it from me to deny to this reasoning such valid- 

 ity as it may fairly claim. Let us endeavour by means 

 of analogy to form a fair estimate of its force. You be- 

 lieve that in society you are surrounded by reasonable 

 beings like yourself. You are, perhaps, as firmly con- 

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