Metaphysics, at least roughly speaking, is the systematic investigation of fundamental presuppositions underlying commonsense and scientific views of the world. Most of us believe that we have bodies and minds, that we are free, that some things in the world are composed of other things and that these things interact causally with one another; we believe that, in addition to the "way things are," there are other ways things could have been, and so on. Common sense tells us that things change and time passes, but contemporary physics tells us (or seems to tell us) that past, present, and...