of the Enlightenment. Although remembered chiefly for his part in the discovery of oxygen, Priestley wrote more extensively on religious, philosophical and educational themes. A nonconformist and eventually a unitarian, he advocated ideals of education and liberalism, based on an associationist psychology and an optimistic belief in the perfectibility of man. His attacks on orthodox religion, and particularly the doctrine of the Trinity led to general horror, and in 1791, after a dissenting celebration of the French Revolution, his house, laboratory, and library were burned by a rampaging patriotic mob. Priestley eventually emigrated to America, where he was befriended by Thomas Jefferson, and founded the first Unitarian church in that country.