What is a definition? A precise and exclusive statement of the essentials of a thing, such that it will fit no other thing. A description may be something altogether different from this. It may so handle the object that the terms are not exclusive at all, but are equally applicable to something else; as here for example, where the phraseology would equally well describe imagination in its more vivid forms--a thing as different as possible from faith. To be quite practical, we have here, if we read this first verse in the light of the whole subsequent development of the chapter, a description of faith at work, of the potency and victories of faith, rather than a definition of faith in its distinctive essence. A true parallel to this passage is the familiar sentence, "Knowledge is power." Those words do not define knowledge, obviously; to do that would demand a totally different phrase. What the words do is to give us one great resultant of knowledge; to tell us that the possession and use of knowledge endows the man who knows with a force and efficiency which he would lack without it. Few words are more elastic and adaptable than the verb substantive. "_Is_" can denote a wide variety of ideas, from that of personal identity, as when I see that yonder distant figure _is_ my brother; to that of equivalence, as when a stamped and signed piece of thin paper called a bank-note _is_ five pounds of gold; or to that of mere representation, as when another piece of paper, or a sheet of canvas, duly lined and coloured by the artist to show the semblance of a human face, _is_ the King, or _is_ my father; or to that of result and effect, as when we say that knowledge _is_ power, or that seeing _is_ believing.[M] [M] It is obvious that these elementary reflections have everything to do with the need of caution in explaining those most sacred words, "This _is_ my body which is given for you." Here we have precisely that last application of the verb substantive, only in an exact and most noble antithesis. "Seeing is believing," says the familiar proverb. "Believing is seeing," says the Divine word here. That is to say, when the human soul so relies upon God that His word is absolute and sufficient for its certainties, this reliance, this faith, has in it the potency of sight. It is as sure of the promised blessing as if it were a present possession. It is as ready to act upon "the things not seen as yet," the laws, powers, hopes beyond the veil, as if all was in open view to the eyes of the body.