"Nothing is more curiously enquired after . . . than the causes of every phenomenon. . . . We] push on our enquiries, till we arrive at the original and ultimate principle. . . . This is our aim in all our studies and reflections."These words sum up David Hume's plan: To discover the fundamental principles at work in the nature and extent of human knowledge, and in so doing to gain a clearer understanding of our perception, ideas (e.g. of cause and...