John Keats coined the term negative capability to describe the willingness to embrace uncertainty, mysteries and doubts.
The first and only time Keats used the phrase was in a letter on 21 December 1817 to his brothers in reference to his disagreement with the English poet and philosopher Coleridge, who Keats believed “sought knowledge over beauty.”
I had not a dispute but a disquisition with Dilke, upon various subjects; several things dove-tailed in my mind, and at once it struck me what quality went to form a Man of Achievement, especially in Literature, and which Shakespeare possessed so enormously – I mean Negative Capability, that is, when a 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. This pursued through volumes would perhaps take us no further than this, that with a great poet the sense of Beauty overcomes every other consideration, or rather obliterates all consideration.
Keats understood Coleridge as searching for a single, higher-order truth or solution to the mysteries of the natural world. He went on to find the same fault in Dilke and Wordsworth. All these poets, he claimed, lacked objectivity and universality in their view of the human condition and the natural world. In each case, Keats found a mind which was a narrow private path, not a “thoroughfare for all thoughts.” Lacking for Keats were the central and indispensable qualities requisite for flexibility and openness to the world, or what he referred to as negative capability.
This concept of Negative Capability is precisely a rejection of set philosophies and preconceived systems of nature. He demanded that the poet be receptive rather than searching for fact or reason, and to not seek absolute knowledge of every truth, mystery, or doubt.
The origin of the term is unknown, but some scholars have hypothesized that Keats was influenced in his studies of medicine and chemistry, and that it refers to the negative pole of an electric current which is passive and receptive. In the same way that the negative pole receives the current from the positive pole, the poet receives impulses from a world that is full of mystery and doubt, which cannot be explained but which the poet can translate into art.
Although this was the only time that Keats used the term, this view of aesthetics and rejection of a rationalizing tendency has influenced much commentary on Romanticism and the tenets of human experience.
For the twentieth-century British psychoanalyst Wilfred Bion, negative capability “was the ability to tolerate the pain and confusion of not knowing, rather than imposing ready-made or omnipotent certainties upon an ambiguous situation or emotional challenge.”
If you're still curious, I recommend reading this thesis on Negative Capability and Wise Passiveness.