 One question that is relevant here is whether time travel is permitted by the prevailing laws of nature. This is presumably a matter of empirical science (or perhaps the correct philosophical interpretation of our best theories from the empirical sciences). But a further question, and one that falls squarely under the heading of philosophy, is whether time travel is permitted by the laws of logic and metaphysics. For it has been argued that various absurdities follow from the supposition that time travel is (logically and metaphysically) possible. Here is an example of such an argument: