For Keats, the avenue to truth and reality took the form of Beauty. The idea, underlying most deeply and consistently the whole of his poetry, is that of the unity of life; and closely allied with this is the belief in progress, through ever-changing, ever-ascending stages. _Sleep and Poetry, Endymion_, and _Hyperion_ represent very well three stages in the poet's thought and art. In _Sleep and Poetry_ Keats depicts the growth even in an individual life, and describes the three stages of thought, or attitudes towards life, through which the poet must pass. They are not quite parallel to the three stages of the mystical ladder marked out by Wordsworth in the main body of his poetry, because they do not go quite so far, but they are almost exactly analogous to the three stages of mind he describes in _Tintern Abbey_. The first is mere animal pleasure and delight in living-- A pigeon tumbling in clear summer air; A laughing school-boy without grief or care Hiding the springy branches of an elm. Then follows simple unreflective enjoyment of Nature. The next stage is sympathy with human life, with human grief and joy, which brings a sense of the mystery of the world, a longing to pierce it and arrive at its meaning, symbolised in the figure of the charioteer. Towards the end of Keats's life this feeling was growing stronger; and it is much dwelt upon in the _Revision of Hyperion_. There he plainly states that the merely artistic life, the life of the dreamer, is selfish; and that the only way to gain real insight is through contact and sympathy with human suffering and sorrow; and in the lost Woodhouse transcript of the _Revision_, rediscovered in 1904, there are some lines in which this point is still further emphasised. The full realisation of this third stage was not granted to Keats during his short life; he had but gleams of it. The only passage where he describes the ecstasy of vision is in _Endymion_ (bk. i., 1. 774 ff.), and this resembles in essentials all the other reports of this experience given by mystics. When the mind is ready, anything may lead us to it--music, imagination, love, friendship. Feel we these things?--that moment have we stept Into a sort of oneness, and our state Is like a floating spirit's. Keats felt this passage was inspired, and in a letter to Taylor in January 1818 he says, "When I wrote it, it was a regular stepping of the Imagination towards a truth."