 In the successive drafts of his Principia, Newton gradually clarified its conceptual structure, and in particular the frame-independent character of its concepts of motion, force, and interaction. He arrived at the new axiomatic structure whose only laws are the familiar “Newton’s Laws of Motion”; the principle of the conservation of the center of gravity, and the relativity principle, were no longer presupposed, but derived from the Laws as Corollaries IV and V: