In his paper, The Paradoxes of Time Travel, David Lewis posits a defense for the possibility of time travel by arguing that the grandfather 'paradox' is not, in fact, paradoxical at all. Two alternative solutions to the grandfather paradox are discussed in this paper. The first is a result of Paul Horwich’s reply to Lewis and aims to pit the Lewisian conception of compatibility against Horwich’s improbability defense. Proposed by Nicholas Smith and C.G. Goddu, this theory explains that any attempt (...) at backward time travel will lead to the creation of long strings of improbable coincidences. An alternative thesis of the multiverse is also discussed, wherein it was proposed that instead of traveling into his past, the time traveler enters an alternate, yet completely identical universe. The multiverse thesis did not stand up to any philosophical critique, and it was posited that the thesis changes the nature of the question entirely. It is evident that Lewis’ discussion of the grandfather paradox raises several fundamentally interesting philosophical questions regarding the logical and causal irregularities of changing the past. This paper aims to adress some of these questions through a metaphysical analysis of Lewis' view, backwards causality, and the nature of time itself. (shrink)

The aim of this paper is to help authors construct coherent time-travel narratives by establishing five features of multiverse time travel. To this end, multiverse time travel will be contrasted to fixed-universe time travel, and both versions related to various cases - where each case is designed to illustrate a key feature of multiverse time travel.