"I am going to talk about what Leibniz and Ernst Mach said about time. ...you can put the Leibnizian/Machian idea into a theory of dynamics, into the way the universe works. ...And the bottom line is this: There is a great likelihood that time does not exist at all, that it is a redundant concept. ...Now for the famous reactions that any of you who have studied the philosophy of science will surely have encountered: The Leibniz-Clarke Correspondence and Ernst Mach's famous book on mechanics. Let me give you some quotations. Leibniz said: "I hold space to be something merely relative." ...His claim is ontological: only relative things exist. ...Only relative changes are real. ...Mach said very similar things many years later."