Well, historically, I'm pretty sure Leibniz published the concepts first, and from who I've spoken too, the educated consensus is that Newton pretty much ripped off Leibniz's work. The problem with debating about what Newton did, is actually Newton himself. He figured out gravity and didn't tell anyone until someone made him do it 3 years later because he was still butt hurt about the situation with Hooke. The guy was an absolute nut. One of, if not the, smartest humans to ever live though. Interesting figure in history.