Job 38:19

Where light dwelleth - What is the source of light? Yea, what is light itself? It is not in the sun, for light was before the sun; but what is light? It is no doubt a substance; but of what kind? and of what are its particles? As to darkness, what is It? Is it philosophical to say, it is the mere privation of light? I shall think philosophy has made some advances to general accuracy and perfection when it proves to us what cold is, and what darkness is, leaving mere privations out of the question.