Principia Book 1 Section 3

At some point I gave up on trying to get the details of each step of each proof and instead just figure out the chain of ideas from one proposition to the next.  Section 2 went from fundamental results that I can articulate to technical results whose motivation was hard to follow at the time.  In fact, even when I think I have unpacked them I then find myself wondering if I am missing the point.  This is not a book that I will be able to digest, only tour. But in section 3 he uses these results to conclude that conic orbits with the sun at the center  imply that objects are attracted to the sun via an inverse square power of the distance from the sun, and that the inverse square law implies Kepler's laws.  That alone would guarantee his immortality, but he still has more to do.  Let's see what he has for us next.