Negative capability was a phrase coined by a Romantic poet J ohn Keats in 1817 to characteriz e the capacity of the greatest writers (particularly Shakespeare) to pursue a vision of artistic beauty even when it leads them into intellectual confusion and uncertainty. Basically this term refers to the "ability of an individual to perceive or think beyond the ways of a predetermined capacity of the human being " .
Keats first used this phrase in a private letter to his brothers, George and Thomas:
" 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—"
Keats view was that one should not go deep to find the reason or solution to the mysteries, doubts or truths of the natural world, ra ther one ought to accept them the way they are and not to become a "thoroughfare for all thoughts".
In English Literature, the examples of Negative Capability can be best found in Keats' own poetry. Keats is basically a poet of imagination. According to him the things we create in our imaginative world to seek pleasure are far from reality, therefore not to find their truth in real world because it will vanish our delight. The ability of discovering beauty in everything overpowers all other considerations.
"Think not of them thou hast thy music too"
In his poetry there is enough of negative capability in Ode to Indolence where the poet is in state of restlessness , uncertainty and doubt. This ode reflects Keats' aversion to action and is an attempt to escape from rigid realities of world. In Ode to Indolence neither love nor ambition, nor poetry seem to be worthwhile to give up the luxurious enjoyment of the moment. He says

__ so sweet as drowsy noons , 
And evenings steep'd in honey'd indolence; 
O, for an age so shelter'd from annoy, 
That I may never know how change the moons, 
Or hear the voice of busy common-sense!

In Ode o n A Grecian Urn , there is an expression of negative capability and this t ime attention of Keats is rivet s on Greek life. The picture of an empty city with its people on their pilgrimage to a shrine is reflection of negative capability of poet.
And, little town, thy streets for evermore 
Will silent be; and not a soul to tell 
Why thou art desolate, can e'er return. 

The same spirit we find in LAMIA. The entire poem is an attempt to fly away from philosophy and scrutinizing eyes of science and philosophy. The contact with reason brings the disappearan ce of lamia, the beautiful serpe nt woman.
In Ode t o Nightingale he becomes the part and parcel of nightingale. He forgets the harsh realities of life and enters the joyous world of nightingale.
Away! Away! for I will fly to thee, 
Not charioted by Bacchus and his pards , 
But on the viewless wings of Poesy, 
Though the dull brain perplexes and retards

The same idea of negative capability can be seen in ENDYMION, particularly in the wandering of shepherd a nd reflection of the spirits is noticed.
In Ode t o Autumn , the poet identifies himself with the spirit of autumn. He becomes a reaper, sitting carelessly on a granary floor. He feels very excited to see the beauty of autumn. He utters

Where are the songs of Spring ? Ay, where are they?

Think not of them, thou hast thy music too,—

Throughout his poetry Keats proposes that beauty is valuable in itself and that it does not need to declare anything for us to know that it is important. That is, beauty does not have to refer to anything beyond itself.
Beauty is truth, truth is beauty -that is all
ye know on earth and all ye need to know
(Ode On A Grecian Urn)