Negative Capability, that is when man is capable of being in uncertainties, mysteries, doubts, without any irritable reaching after fact and reason—Coleridge, for instance, would let go by a fine isolated verisimilitude caught from the penetralium of mystery, from being incapable of remaining content with half knowledge.

letter to George and Thomas Keats, 21 December 1817, in H. E. Rollins (ed.) Letters of John Keats (1958) vol. 1