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time travel. the grandfather paradox ii. Tim can kill Grandfather. Tim cannot kill Grandfather. lewis’s puzzle. Hud works with those people. Hud doesn’t work with those people. lewis’s puzzle. Hud works with Dan and Frances. Hud doesn’t work with Ben and Zoe. lewis’s puzzle.
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time travel the grandfather paradox ii
Tim can kill Grandfather. • Tim cannot kill Grandfather. lewis’s puzzle
Hud works with those people. • Hud doesn’t work with those people. lewis’s puzzle
Hud works with Dan and Frances. • Hud doesn’t work with Ben and Zoe. lewis’s puzzle
Tim can kill Grandfather. • Tim cannot kill Grandfather. lewis’s puzzle
Tim’s killing Grandfather is compossible with the R facts. • Tim’s killing Grandfather is not compossible with the R+ facts. lewis’s puzzle
A’s X-ing is compossible with facts F1-Fniff there is some possible world in which F1-Fn obtain and A Xs. lewis’s puzzle
If time travel is possible, then one can change the past. • One cannot change the past. • [So] Time travel is not possible. the altered past paradox
It is either true that Hud will eat dinner tonight or true that Hud won’t eat dinner tonight. • If it is true that Hud will eat dinner tonight, then his eating dinner is unavoidable. • If it is true that Hud won’t eat dinner tonight, then his not eating dinner is unavoidable. • [So] Whatever happens—dinner or no dinner—is unavoidable. the fatalist argument
If time travel is possible, then one can commit retro-suicide. • One cannot commit retro-suicide. • [So] Time travel is not possible. the retro-suicide paradox