This authoritative, modern translation by Cohen and Whitman, the first in over 285 years, is based on the 1726 edition, the final revised version approved by Newton; it includes extracts from the earlier editions, corrects errors found in earlier versions, and replaces archaic English with contemporary prose and up-to-date mathematical forms. The illuminating Guide to the Principia by I. Bernard Cohen, along with his and Anne Whitman's translation, make this preeminent work truly accessible for today's scientists, scholars, and students.