This is a good book. Hawley writes very clearly, her book is authoritative and well-argued.



Hawley's strategy has two parts: first, with a "divide-and-conquer" method she wants to show that four-dimensionalism is more plausible than three-dimensionalism, and that her own version of four dimensionalism (stage theory) is better than perdurantism. Four-dimensionalism is the thesis that physical objects persist in virtue of having temporal (as well as spatial) parts. This is an elegant and popular solution of the problem of change. The problem is how to accommodate Leibniz's Law with the fact that things change. Four-dimensionalism says that since any Objects O persists from time t1 to t2 by having a part O(t1) and O(t2), and O(t1) and O(t2) have different properties, they are therefore different objects and don't violate Leibniz's Law.

Hawley's own version of four-dimensionalism is stage theory. Stage theorists hold that strictly speaking temporal parts don't make up a perduring object; when we refer to a physical object, we refer to an actual temporal part of it. Hence we cannot refer to the same object at two different times, at least not if 'the same' means 'identical'. Hawley's arguments for stage theory are based largely on considerations about the philosophy of language.



The second type of Hawley's arguments claim that from all theories of persistence, stage theory is the only one that doesn't commit one to restricted views about other metaphysical issues. For instance, stage theory is compatible with most theories of vagueness and modality. These are perhaps the most sophisticated and developed parts of the book.



interestingly the book doesn't start very promising, but towards the end it gets better and better. The only weakness is that sometimes she dismisses three-dimensionalist explanations too quickly. Hawley's views are often contraintuitive, but she is smart (in the good sense) in explaining philosophical worries away. I recommend this book for everyone interested in the metaphysics of persistence.