Hume's Treatise was published before he was thirty (after its publication in 1739-40 he wrote that it 'fell dead-born from the press'). It is nothing less than an attempt to extend the Copernican Revolution to philosophy - to put to the test of experience a complete system of the moral sciences which had hitherto gone unquestioned. But Hume was no rationalist: from his viewpoint of informed scepticism he could see man not as a religious creation, nor as a machine, but as a creature dominated by sentiment, passion and appetite. With justice Sir Isaiah Berlin has written of him: 'No man has influenced the history of philosophy to a deeper or more disturbing degree.'