In F. R. Leavis's view, two essential aspects of Keats's greatness are his aestheticism and the degree to which the poet's personality disappears from his poetry. Keats's poetry, for Leavis, is based on an ethic of "art for art's sake"; instead of trying to convince us of philosophical or moral truth, he seeks to stimulate our imagination and our senses. This is also related to Keats's concept of negative capability, in which the poet creates from a position of doubt and uncertainty. The ideal, for Keats and for Leavis, is for the personality, ideas, and convictions of the poet to disappear completely, so that when we are reading a poem, we are not even sure what the author believes or intends for us to glean from the poem. Keats, more than any other poet, embodies this ideal of the "chameleon poet," as he put it one of his letters. For Leavis, this is the key to explaining his greatness.