Montaigne 1.24
Now, I say that not only in medicine, but in several more certain arts, there is a good deal of luck. Why should we not attribute the poetic flights which ravish and transport their author out of himself to his good luck, since he himself confesses that they exceed his power and ability, and acknowledges them to proceed from something else than himself, and to be no more within his power than those extraordinary emotions and agitations of orators, which, as they say, impel them beyond their intention?
It is the same with painting, for it sometimes happens that touches escape from the brush of the artist that so far exceed his conception and his art as to excite his own admiration and astonishment. But Fortune still more evidently shows the share that she has in all these works, buy the charm and beauty which enter into them, not only in spite of the intention, but without even the knowledge of the workman. A competent reader will often discover in the writings of others perfections other than their author intended or perceived, and lend them a fairer face and a richer meaning (123f.)