Art is in the world but not of it; it lives in a kingdom of its own, governed by laws that none but artists can understand.
 Samuel Butler, The Note-Books of Samuel Butler (1912). copy citation

Context

“it is persevered in as long as body and soul can be kept together, whether there be pay or no, and perhaps better if there be no pay. Nevertheless, though art disregards money and trade disregards art, the artist may stand not a little trade-alloy and be even toughened by it, and the tradesmen may be more than half an artist. Art is in the world but not of it; it lives in a kingdom of its own, governed by laws that none but artists can understand. This, at least, is the ideal towards which an artist tends, though we all very well know we none of us reach it. With the trade it is exactly the reverse; this world is, and ought to be, everything, and the invisible world is as little to the trade as this visible world is to the artist.” source