At the time of his death in 1996, our colleague Sam Westfall had begun to plan a Newton volume for the Cambridge Companions series. He had made contact with potential contributors, but had not reached the final stages of planning. When Cambridge University Press invited us to succeed Sam as editors of this volume, we received generous help from his wife, Gloria. For this we are profoundly grateful. Studying Sam's preliminary table of contents revealed to us that his orientation to a book for this series, though reflecting his deep scholarship, was nevertheless entirely different from ours. For practical purposes, therefore, we started afresh. Still, it was a source of constant regret that we could not draw on Sam's wisdom and knowledge of Newton, a loss aggrandized by the tragic early death of Betty Jo Teeter Dobbs.
Our original plan for this book included a chapter on the reception and assimilation of Newton's science among late-seventeenthand eighteenth-century philosophers. Two considerations led us to abandon this plan and restrict attention to philosophers with whom Newton actually interacted, most notably Leibniz. First, the number of philosophers such a chapter ought to examine is too large, and their individual responses to Newton are too diverse, to be manageable within the scope of one or two chapters of reasonable length. Second, many of these responses shed more light on the philosopher in question than on Newton, often because they are responses to a caricature of Newton's science. There is a book to be written that examines philosophers' reactions to Newton's science from Locke through Kant (if not through Mill and Whewell, or even Mach), carefully comparing their construals of that science both with what