5 July 1687 July 4, 2015 Author: Staff Isaac Newton publishes Philosophiæ Naturalis Principia Mathematica. Famous Words of Inspiration..."No man is happy who does not think himself so." Publilius Syrus — Click here for more from Publilius Syrus Related posts: 5 July 1687 17 October 1979 4 July 1569 5 July 1948 5 July 1948 5 July 1946 Categories: History Tags: 1687, 5 July