3 Joseph Priestley, Metaphysician and Philosopher of Religion

Abstract This chapter examines Priestley's philosophical thought. It argues that Priestley's chief importance as a philosophical theorist lies in keeping alive, clarifying, and deepening lines of thought under threat of being marginalized as the exclusive preserve of unbelievers. His championing of the cause of necessity made it easier to entertain such a view impartially and more difficult to dismiss it out of hand. His spirited defence of the doctrines of necessity and materialism has been singled out for praise by the likes of the Victorian scientist T. H. Huxley, who found his ‘among the most powerful, clear, and unflinching expositions of materialism and necessarianism which exist in the English language’. As James Harris observes, Priestley's formulation of the doctrine of necessity became the point of departure for defenders of necessity for the next forty years in Britain, particularly among dissenters. As for his third major philosophical interest — the association of ideas — he served as a champion of Hartley through his edition, but the loss of his manuscript during the Birmingham riots meant that this potential legacy was left unrealized.