Keats and his friends, poets, critics, novelists, and editors wrote to each other daily, and Keats' ideas are bound up in the ordinary, his day-to-day missives sharing news, parody and social commentary. They glitter with humour and critical intelligence. Born of an "unself-conscious stream of consciousness," they are impulsive, full of awareness of his own nature and his weak spots. When his brother George went to America, Keats wrote to him in great detail, the body of letters becoming "the real diary" and self-revelation of Keats' life, as well as containing an exposition of his philosophy, and the first drafts of poems containing some of Keats' finest writing and thought. Gittings describes them as akin to a "spiritual journal" not written for a specific other, so much as for synthesis. Keats also reflected on the background and composition of his poetry, and specific letters often coincide with or anticipate the poems they describe. In February to May 1819 he produced many of his finest letters". Writing to his brother George, Keats explored the idea of the world as "the vale of Soul-making", anticipating the great odes that he would write some months later. In the letters, Keats coined ideas such as the Mansion of Many Apartments and the Chameleon Poet, concepts that came to gain common currency and capture the public imagination, despite only making single appearances as phrases in his correspondence. The poetical mind, Keats argued:  has no self – it is every thing and nothing – It has no character – it enjoys light and shade;... What shocks the virtuous philosopher, delights the camelion [chameleon] Poet. It does no harm from its relish of the dark side of things any more than from its taste for the bright one; because they both end in speculation. A Poet is the most unpoetical of any thing in existence; because he has no Identity – he is continually in for – and filling some other Body – The Sun, the Moon, the Sea and Men and Women who are creatures of impulse are poetical and have about them an unchangeable attribute – the poet has none; no identity – he is certainly the most unpoetical of all God's Creatures. 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 ...[Being] content with half knowledge" where one trusts in the heart's perceptions.