 Thus Newton repeats the view he mentions to Leibniz in 1693, viz., that the force of gravity itself causes the planets to follow their orbital paths rather than their inertial trajectories along the tangents to those orbits, independently of any fluid medium in the heavens. But in this posthumously published letter, Newton did not merely repeat his basic understanding of gravity from his 1693 exchange with Leibniz; he also included a wider discussion of mechanist norms within philosophy more generally. Again, Newton begins by quoting Leibniz: