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 point 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 Berline has written of him: 'No man has influenced the history of philosophy to a deeper or more disturbing degree.'