SCIENTIFIC USE OF THE IMAGINATION 115 



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 phenomena of light which ordi- 

 nary knowledge and skilled experiment reveal. If in all 

 the multiplied varieties of these phenomena, including 

 those of the most remote 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 agreement 

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

 Eefraction and in other cases, it actually forces upon our 

 attention phenomena which no eye had previously seen, 

 and which no mind had previously imagined — such a con- 

 ception must, we think, be something more than a mere 

 figment of the scientific fancy. In forming it, that com- 

 posite and creative power, in which reason and imagina- 

 tion are united, has, we believe, led us into a world not 

 less real than that of the senses, and of which the world 

 of sense itself is the suggestion and, to a great extent, the 

 outcome. 



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

 movably 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 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 analogy, to 

 form a fair estimate of its force. You believe that in so- 

 ciety you are surrounded by reasonable beings like your- 

 self. You are, perhaps, as firmly convinced of this as of 



