The letters of this date should be read and re-read by all who want to get to the centre of Keats's mind or to hold a key to the understanding of his deepest poetry. The richest of them all is that in which he sends the fragments of an ode to Maia written on May day with the (alas! unfulfilled) promise to finish it 'in good time.' The same letter contains the re-assertion of a purpose declared in a letter of a week before to Mr Taylor in the phrases, 'I find I can have no enjoyment in the world but the continual drinking of knowledge. I find there is no worthy pursuit but the idea of doing some good to the world.... There is but one way for me. The road lies through application, study and thought. I will pursue it.' The mood of the verses interpreting the song of the thrush a few weeks earlier has passed, the reader will note, clean out of the poet's mind. To Reynolds his words are:-- An extensive knowledge is needful to thinking people--it takes away the heat and fever; and helps, by widening speculation, to ease the Burden of the Mystery, a thing which I begin to understand a little, and which weighed upon you in the most gloomy and true sentence in your letter. The difference of high Sensations with and without knowledge appears to me this: in the latter case we are falling continually ten thousand fathoms deep and being blown up again, without wings, and with all [the] horror of a bare-shouldered creature--in the former case, our shoulders are fledged, and we go through the same air and space without fear. Let it never be forgotten that 'sensations' contrasted with 'thoughts' mean for Keats not pleasures and experiences of the senses as opposed to those of the mind, but direct intuitions of the imagination as opposed to deliberate processes of the understanding; and that by 'philosophy' he does not mean metaphysics but knowledge and the fruits of reading generally. The same letter, again, contains an interesting meditation on the relative qualities of genius in Milton and Wordsworth as affected by the relative stages of history at which they lived, and on the further question whether Wordsworth was a greater or less poet than Milton by virtue of being more taken up with human passions and problems. This speculation leads on to one of Keats's finest passages of life-wisdom:--