We must conclude, from the above discussion, that Putnam has not satisfactorily explained how a person can go back in time and thus has not offered any compelling reason why we should accept his description of Oscar rather than his objector's description. However, earlier in our discussion, a possible way to show that Oscar did go back in time came to light: namely, if it could be shown that Oscar2 was at B at t 1 because Oscar1 entered the time (...) machine at t 2. Thus, if backward causation were possible, such backward causes could be used to send a person back in time. But whether backward causation is a conceptual possibility or not is the topic for another paper. (shrink)

Gödel's conclusion that time-travel is possible in his models of Einstein's gravitational theory has been questioned by Chandrasekhar and Wright, and treated as doubtful in the recent philosophical literature. The present note is intended to remove this doubt: a review of Gödel's construction shows that his arguments are entirely correct; and the objection is seen to rest upon a misunderstanding. Computational points treated succinctly by Gödel are here presented in fuller detail. The philosophical significance of Gödel's results is briefly considered, (...) and a set of technical questions is posed whose answers would clarify this significance. (shrink)

Sometimes also called retro causation. A common feature of our world seems to be that in all cases of causation, the cause and the effect are placed in time so that the cause precedes its effect temporally. Our normal understanding of causation assumes this feature to such a degree that we intuitively have great difficulty imagining things differently. The notion of backward causation, however, stands for the idea that the temporal order of cause and effect is a mere contingent feature (...) and that there may be cases where the cause is causally prior to its effect but where the temporal order of the cause and effect is reversed with respect to normal causation, i.e. there may be cases where the effect temporally, but not causally, precedes its cause. (shrink)