If a man would enter into ‘Noah’s rainbow,’ he has written, and ‘make a friend’ of one of ‘the images of wonder’ which dwell there, and which always entreat him ‘to leave mortal things,’ ‘then would he arise from the grave and meet the Lord in the air’; and by this rainbow, this sign of a covenant granted to him who is with Shem and Japhet, ‘painting, poetry and music,’ ‘the three powers in man of conversing with Paradise which the flood “of time and space” did not sweep away,’ Blake represented the shapes of beauty haunting our moments of inspiration: shapes held by most for the frailest of ephemera, but by him for a people older than the world, citizens of eternity, appearing and reappearing in the minds of artists and of poets, creating all we touch and see by casting distorted images of themselves upon ‘the vegetable glass of nature’; and because beings, none the less symbols, blossoms, as it were, growing from invisible immortal roots, hands, as it were, pointing the way into some divine labyrinth. If ‘the world of imagination’ was ‘the world of eternity,’ as this doctrine implied, it was of less importance to know men and nature than to distinguish the beings and substances of imagination from those of a more perishable kind, created by the phantasy, in uninspired moments, out of memory and whim; and this could best be done by purifying one’s mind, as with a flame, in study of the works of the great masters, who were great because they had been granted by divine favour a vision of the unfallen world from which others are kept apart by the flaming sword that turns every way; and by flying from the painters who studied ‘the vegetable glass’ for its own sake, and not to discover there the shadows of imperishable beings and substances, and who entered into their own minds, not to make the unfallen world a test of all they heard and saw and felt with the senses, but to cover the naked spirit with ‘the rotten rags of memory’ of older sensations. The struggle of the first part of his life had been to distinguish between these two schools, and to cleave always to the Florentine, and so to escape the fascination of those who seemed to him to offer the sleep of nature to a spirit weary with the labours of inspiration; but it was only after his return to London from Felpham in 1804 that he finally escaped from ‘temptations and perturbations’ which sought to destroy ‘the imaginative power’ at ‘the hands of Venetian and Flemish Demons.’ ‘The spirit of Titian’—and one must always remember that he had only seen poor engravings, and what his disciple, Palmer, has called ‘picture-dealers’ Titians’—‘was particularly active in raising doubts concerning the possibility of executing without a model; and when once he had raised the doubt it became easy for him to snatch away the vision time after time’; and Blake’s imagination ‘weakened’ and ‘darkened’ until a ‘memory of nature and of the pictures of various schools possessed his mind,