Within months after the Principia was published in the summer of 1687, Newton was elected to represent Cambridge in Parliament, with William and Mary assuming the throne of England. Over the years between 1687 and 1693, he was anything but housebound. Indeed, he spent somewhere around a month visiting John Locke, who was living in the home of his long time friend, Lady Masham, where the three of them appear to have engaged in long philosophical discussions.
Myths about Newton abound. The idea that he withdrew from the world following the publication of the Principia seems to me to have less substance behind it than most.
George E. Smith, Acting Director' The Dibner Institute for the History of Science and Technology MIT E56-100 Cambridge, MA 02139