| This dissertation addresses questions about the three-fold relationship between possibility, possible worlds , and the structure of this world.;David Lewis's theory of counterparts says the different ways you could have been are not different possible worlds in which you are different, but rather different possible individuals which represent you. This theory faces a technical problem: it isn't clear how the theory can make sense of claims about actuality—for instance, the claim that there could have been more things than there actually are. Straightforward reasoning about counterparts and actuality seems to lead to unacceptable consequences. I show that, by paying careful attention to the relation that holds between possible individuals and the actual things they represent, this technical challenge can be met.;But the solution brings another puzzle into focus. According to Lewis, sometimes a single possible world underlies two ways you could be. So possible worlds come apart from ways things could be. How can this be, if possible worlds were introduced for the sake of reasoning about what could be? The answer, I argue, comes from distinctively metaphysical concerns. Metaphysical inquiry distinguishes the way things are in a “thin” deflationary sense from the way the WORLD is, in a “thick” metaphysical sense. This distinction gives rise to a parallel distinction between “thin” ways things could be and “thick” ways the WORLD could be. This helps make sense of Lewis's doctrine, and links it to “first-order” questions about the metaphysics of individuals.;I then apply these considerations to the metaphysics of space and time. In famous correspondence, Leibniz and Clarke disputed the doctrine that “space is a real and absolute being”, reasoning from premises about how material things could have been shifted from where they actually are. I argue that a “Leibniz shift” style argument is sound, and pushes us toward a revised spatiotemporal metaphysic. In this argument, possible worlds —understood as possibilities concerning the objective WORLD—cannot be dispensed with for considerations merely about what could have been. Finally, I sketch a new spacetime theory which is immune to such shifts. |
