He used the term negative capability to discuss the state in which we are "capable of being in uncertainties, Mysteries, doubts without any irritable reaching after fact & reason ... content with half knowledge" where one trusts in the heart's perceptions. He wrote later: "I am certain of nothing but the holiness of the Heart's affections and the truth of Imagination – What the imagination seizes as Beauty must be truth – whether it existed before or not – for I have the same Idea of all our Passions as of Love they are all in their sublime, creative of essential Beauty" again and again turning to the question of what it means to be a poet. "My Imagination is a Monastery and I am its Monk", Keats notes to Shelley. In September 1819, Keats wrote to Reynolds "How beautiful the season is now – How fine the air. A temperate sharpness about it... I never lik'd the stubbled fields as much as now – Aye, better than the chilly green of spring. Somehow the stubble plain looks warm – in the same way as some pictures look warm – this struck me so much in my Sunday's walk that I composed upon it". The final stanza of his last great ode, "To Autumn", runs: