This book is a defense of modal realism; the thesis that our world is but one of a plurality of worlds, and that the individuals that inhabit our world are only a few out of all the inhabitants of all the worlds. Lewis argues that the philosophical utility of modal realism is a good reason for believing that it is true.

E. J. Lowe; The problems of intrinsic change: rejoinder to Lewis, Analysis, Volume 48, Issue 2, 1 March 1988, Pages 72–77, https://doi.org/10.1093/analys/48.2.7.

This article characterizes the varieties of four - dimensionalism and provides a critical overview of the main arguments in support of it.

A solution to the problem of intrinsic change for enduring things should meet three conditions. It should not replace monadic intrinsic properties by relations. It should not replace the having simpliciter of properties by standing in some relation to them. It should not rely on an unexplained notion of having an intrinsic property at a time. Johnston's solution satisfies the first condition at the expense of the second. Haslanger's solution satisfies the first and second at the expense of the third.

Four dimensionalism, as it will be understood in this article, is a view about the ontological status of non-present objects. Presentists say that only present objects exist. There are no dinosaurs, though there were such things; there are no cities on Mars, though perhaps there will be such things. Four-dimensionalists, on the other hand, say that there are past or future objects (or both); and in saying this, they mean to put such things ontologically on a par with present objects. (...) According to the four-dimensionalist, non-present objects are like spatially distant objects: they exist, just not here, where we are. (shrink)