Times Literary Supplement, No. 5521 (January 23, 2009): 24. Something to go on Trenton Merricks Eric T. Olson WHAT ARE WE? A Study in Personal Ontology 259 pp. Oxford University Press. £23.99 (US $39.95). 978 0 19 517642 1 Eric T. Olson asks: What Are We? One might answer: Britons. Or Americans. Or philosophers. Or farmers. Or dog lovers. Or cat people. But these very natural answers would show that one has misunderstood Olson's question. A less natural, but more appropriate, answer would be living human bodies. Or non-physical spiritual substances. Or psychological events, akin to computer programs running on the 'hardware' of our brains. Or brains themselves. Considering these appropriate answers to Olson's question-and considering that they are indeed appropriate-is the easiest way to understand that question. So it is the easiest way to understand 'personal ontology', which is that part of philosophy concerned with answers to Olson's question. Olson discusses the appropriate answers just noted, and others, and assesses their strengths and weaknesses. But before we can evaluate these answers, we must first understand them. And the best way to understand any account of personal ontology is to consider, as Olson does, its implications. For example, if we are spiritual substances, the possibility of life after death is fairly straightforward. After all, if you are a spiritual substance, then your body is not 2 you. So there is no reason that when your body ceases to exist, such as by cremation, you should cease to exist. On the other hand, if you are your living body, then the destruction of your body is the destruction of you. When it ceases to exist, you cease to exist. For you to live again, that very body (that is, you) would have to come back into existence and live again: a bodily resurrection. The question of what it would take to survive the death and destruction of our bodies is one particularly sensational example of a more general question, the question of personal identity over time. This is the question of how a person now existing manages to be the same person as some future (or past) person. Since the time of John Locke, the dominant view has been that personal identity over time occurs in virtue of the occurrence of some sort of psychological continuity, with memory playing the key role. So, for example, if a future person has memories of my current experiences, then that future person is who I will be. The topic of identity over time has received more attention than, and has been pursued largely independently of, Olson's topic of personal ontology. Those who have read Olson's book will know that this is a mistake. For example, suppose that your memories are somehow transferred from your original body to a new body. (Olson imagines this happening by way of your cerebrum's being taken from your original head and transplanted into the head of a new body.) According to the psychological continuity view, you would then leave your body behind. This implies straightaway that you are not your body, since your body cannot possibly leave itself behind. As a result, the psychological view is not consistent with the claim that you are your body. So arguments 3 for the psychological view are arguments against one answer to Olson's question, the answer that we are our bodies. Conversely, if we are our bodies, the psychological continuity view of personal identity over time is false. So any argument for the claim that we are our bodies is an argument against the psychological continuity view. All of this reinforces the point already illustrated by the example of life after death. That point is that the question of personal identity over time goes hand in hand with the question of personal ontology, and neither should be approached in isolation of the other. Olson makes this point convincingly again and again. Olson's book is not the first book to show that personal ontology bears on personal identity over time, and vice versa. But this book's main contribution is not the originality of this, or of any other, isolated point. Rather, its main contribution is its comprehensive vision. In this book, Olson presents all the serious options on personal ontology. And he presents the best reasons for and against each of these options. And he shows that each of these options has implications for a wide variety of philosophical topics-not just personal identity over time-and also that those topics have implications for each of these options. No other book does all of this. Moreover, Olson's book is clear enough to be of use to the philosophical novice, but sophisticated enough and fair enough to withstand the scrutiny of professional philosophers. For anyone who wants to understand the question 'What are we?'-and who wants to see how to begin to answer that question in a principled way-there is no better guide than Olson's excellent book. And once we understand this question, it is hard to see why we were not asking it all along. 4 Trenton Merricks is Professor of Philosophy at the University of Virginia and the author of Objects and Persons, 2001 and Truth and Ontology, 2007.