Response To David Lewis Parallel Universe Theory

Contrary to the parallel universe theory, David Lewis comes up with a solution of his own—a solution to the grandfather paradox. He explains that the diction in the paradox is quite important. Saying that Tim can kill his grandfather doesn’t necessarily mean he did kill his grandfather. If Tim were to go back in time and try to kill his grandfather “conditions are perfect in every way for him to do so” but it doesn’t mean he will go through and do it. It’s sort of like saying, I can speak Portuguese if I really want to, but that doesn’t mean I know the language enough to speak it. Comparing it to say a dog, which has the biological incapability to learn Portuguese all together. He also states that by saying Tim can kill his grandfather, we also have to say that Tim can’t kill his grandfather.

That’s because Tim is alive, and didn’t alter the outcome. If Tim’s grandfather is already dead, and Tim wanted to kill him before he died on his own, then Tim would have to go back in time before his grandfather died from natural cause. But, because we know his grandfather died in year x, then even if he does try to go back to before time x, he wouldn't be successful in killing him because we know he died in time x and not before x. In page 5 of The Paradoxes of Time Travel, Lewis states that “events of a past moment are not sub-divisible into temporal parts, and therefore cannot change meaning that what happened in the past is already known as a fact, so those moments cannot assume a different time dimension. It’s usually referring to time travel in the past instead of traveling in the