A Nonlinear History of Time Travel - Issue 40: Learning

I doubt that any phenomenon, real or imagined, has inspired more perplexing, convoluted, and ultimately futile philosophical analysis than time travel has. In his classic textbook, An Introduction to Philosophical Analysis, John Hospers tackles the question: "Is it logically possible to go back in time--say, to 3000 B.C., and help the Egyptians build the pyramids? We must be very careful about this one." It's easy to say--we habitually use the same words to talk about time as we do when talking about space--and it's easy to imagine. "In fact, H. G. Wells did imagine it in The Time Machine (1895), and every reader imagines it with him." Hospers was a bit of a kook, actually, who achieved the unusual distinction for a philosopher of having received one electoral vote for President of the United States. But his textbook, first published in 1953, remained standard through four editions and 40 years. His answer to the rhetorical question is an emphatic no. Time travel à la Wells is not just impossible, it is logically impossible. It is a contradiction in terms. In an argument that runs for four dense pages, Hospers proves this by power of reason. "How can we be in the 20th century A.D. and the 30th century B.C. at the same time? Here already is one contradiction … It is not logically possible to be in one century of time and in another century of time at the same time."