Why Time Travel is not Paradoxical according to David Lewis Essay Example for Free

Why Time Travel is not Paradoxical according to David Lewis Essay The grandfather paradox is one of the most well known examples of a paradox associated with time travel. Supposing that a person, say Henry, wants to kill his grandfather, and Henry wants to travel back in time to do so. If Henry does succeed in killing his grandfather at a time when the grandfather has not yet fathered the offspring that would eventually become Henry’s parent, then Henry would never have been born in the first place, so how could he have traveled back in time? David Lewis argues that time travel is not paradoxical. His answer to the grandfather paradox is that, in the first place, Henry would not have been able to kill the grandfather. In other words, a time traveler who goes back to the past cannot change the past. According to Lewis, Henry—or any time traveler—would simply be part of the reality of the past. Henry would be part of the past as a time traveler—in other words, there is only one past in the first place, and that past has always included the time traveler Henry. Thus, there are no changes that can be done to the past, because the fact that he time-traveled would have been true even before he decided to do it, and even before he existed. Every point in time is equally real, and nothing can change it. Another paradox is the causal loop, to which Lewis’ solution applies as well. An example of a causal loop is when a person receives the plans for a time machine from a mysterious stranger. This person creates the time machine, travels back in time, and gives his younger self the plans. The problem here is the origin of the time machine plans. Where did they come from? According to Lewis, the plans would simply have had no cause, in the same way that the universe, or God, exists uncaused.