Peter van Inwagen and Dean Zimmerman have edited a fine collection of fifteen essays at the intersection of the philosophy of God and the philosophy of mind, dedicated to the late Philip L. Quinn. The work as a whole provides some reason for thinking that philosophical reflection on God and human nature should be intertwined. Alvin Plantinga and several other contributors employ arguments based on their Christian theism for certain tenets in philosophy of mind and Brian Leftow draws on some models of personal identity in philosophy of mind to shed light on a Trinitarian concept of God. The contributors differ substantially in their metaphysics (idealism, dualism, and physicalism are each represented), but they have close to a consensus when it comes to accepting theism.

In the introduction Zimmerman addresses theologians who may be put off by the analytic methodology of most contributors. Under the heading ‘What analytic philosophy is, was, and wasn't’, Zimmerman challenges the assumption that ‘the analytic river is still patrolled by theologian-eating sharks’ (7). He reports that the waters are much safer, at this point, and under the heading ‘The need for cooperation’, Zimmerman urges theologians and philosophers to work on joint projects. This call for co-operation is (in my view) laudatory, though the book itself does not contain work by theologians (unless one is counting philosophical theologians) and the analytic style of, say, John Hawthorne's meticulous, formal reconstruction of Descartes' view of attributes is more in keeping with a logic or mathematics journal than current theological literature. Zimmerman devotes a significant part of the introduction to the status of mind–body dualism. I shall follow his lead and begin with a survey of how Persons addresses the debate over dualism and its chief rivals.

Zimmerman is one among a growing number of philosophers who think that ‘dualism still belongs on the table’ of live options in philosophy of mind (13). He does not think that Ockham's Razor, appeals to the conservation of energy, or the critiques of dualism one finds in Dennett et al. are at all decisive, let alone persuasive. I believe Dennett is rightly castigated for his question-begging characterization of dualism that makes it, by definition, anti-scientific. An additional point that might have been good to make contra Dennett is that he assumes a problem-free concept of the physical world. Dennett thinks that we should begin with a physicist account of the brain and only then turn to posit a self or soul (which, for Dennett, is the equivalent to positing a ghost) if that is required to account for brain, or some other physical, activity. Dennett claims: ‘A ghost in the machine is of no help in our theories unless it is a ghost that can move things around … but anything that can move a physical thing is itself a physical thing (although perhaps a strange and heretofore unstudied kind of physical thing)’ (cited by Zimmerman, 23).

But the case for dualism actually works quite differently: most dualists historically and today begin with what appears to be the case from the first-person perspective. Arguably, we have experiences of the world and seem to move things around. As R. M. Adams argues in the first chapter in Persons, our experience of the world around us is thoroughly mental. In ‘Idealism vindicated’, Adams may or may not go too far in his case for a Berkleyan metaphysics and epistemology, but his insistence upon the primacy of the mental is forceful. If we are taking dualism seriously (something Dennett rarely does) then the line of reasoning needs to be altered to something like this: we have experiences and move things around. Could it be that these activities and undertakings are the very same thing that a physicist identifies as brain states or some other bodily states and activities, or perhaps some other kind of thing?

Without trying to answer that question here, it is worth pointing out the vast difference between Dennett and the theologian-eating philosophers of a previous generation. The verificationists like A. J. Ayer may have sought to dispatch religious language as non-cognitive, but they were not in doubt of the primacy of the mental and the difficulty of identifying the mental with bodily, physical states. I cite A. J. Ayer in an interview near the end of his life where he concedes the faults in his early verificationism but objects to those, like Gilbert Ryle (whom Dennett has described as his mentor) who believe they have shown dualism to be the equivalent of believing in ghosts.

Ayer's case for dualism is constructive to consider in reference to critiques of dualism beyond Dennett. So, for example, Van Inwagen thinks it may be puzzling to consider how a physical thing thinks, but he claims it is equally puzzling to consider how a non-physical thing thinks. The case for dualism proceeds differently: it is not as though the dualist considers some physical and non-physical things and then matches them up, concluding that thinking must be undertaken by a non-physical thing. Rather, dualists are convinced that thinking exists (and, typically, that there is a self) and then they reject the identity between thinking and physical states and things. Dualists maintain a positive view of the mental and then contend that its nature is not the very same as a physical state. Their line of reasoning is akin to Platonists who conclude that there are abstract, non-physical objects like properties, not because they examine a bunch of physical things and non-physical things, and conclude that properties must be the latter; rather, they reason that properties exist and cannot by physical.

Plantinga's chapter 4, ‘Materialism and Christian belief,’ is the longest in the volume and centres around two arguments for dualism, and some replies to a series of objections to dualism. Plantinga's first argument employs the principle of the indiscernability of identicals, and concludes that persons are not identical with their bodies because a person can survive the gradual replacement of all his or her bodily parts. This is an example of the well-known modal argument for dualism. It is curious that Plantinga advocates this argument while adopting a general scepticism about modal claims based on imaginability and conceivability. Plantinga writes:

How can Plantinga ‘speak just of possibility’ or assert that we have a fundamental epistemic modal power without assuming some principle to the effect that if we seem to be able to imagine (‘conceive, picture, describe’, or, to use Plantinga's terminology, ‘consider’ or ‘envisage’) some state of affairs, and see no contradiction in the state of affairs, or see that it is compatible with what we have reason to believe is necessary, then we are prima facie justified in believing that state of affairs to be possible? Plantinga later makes dramatic claims about what he believes to be imaginable:

I suspect Plantinga is too cavalier here. In his last claim, perhaps Plantinga is using ‘imagine’ in the sense that imagination requires mental imagery (and if so, I agree that many things can be conceived of that are not imaginable in the sense that we can form no image or picture of the state of affairs). But I do not know anyone who, like Plantinga, is a Platonist and believes that by imagining a sentence (a physical inscription) is red, he has thereby imagined that a non-physical abstract object is red. And imagining an elephant forming a sentence is not to imagine a non-physical abstract object is an animal of any sort. Plantinga cites approvingly David Kaplan's flippant comment that he could imagine refuting Godel's incompleteness theorem by imagining a newspaper headline: ‘UCLA PROF REFUTES GODEL; ALL REPUTABLE EXPERTS AGREE’ (115). But any claim to imagine clearly and distinctly such a refutation is about as serious as my claiming to imagine making a round square by picturing this headline: ‘TALIAFERRO MAKES A CLOSED TWO-DIMENSIONAL OBJECT THAT HAS AND DOES NOT HAVE FOUR RIGHT ANGLES’. I suggest that in much of his work Plantinga (as well as other modal sceptics like Van Inwagen) rely on conceivability as a guide to possibility, and that if they truly dispensed with imaginability or conceivability as a guide to possibility much of their work would be undermined. (For a defence of this claim, see my ‘ Sensibility and possibilia: a defence of thought experiments’, Philosophia Christi, 3 (2003), 403–420.)

When Persons is not friendly toward dualism, it includes some creative forms of physicalism. Plantinga's second dualist argument revives a Leibnizian thesis that one may see that thinking is not (and could not be) the same thing as physical states and processes. In chapter 5 Richard Swinburne offers a defence of substance rather than merely property dualism. In ‘The self and time,’ Howard Robinson offers some reasons for thinking that selves do not endure through time on a metric scale but enjoy atemporal endurance. Van Inwagen devotes much of his chapter exposing ‘the metaphysical confusions into which … many materialists have fallen’ (206). The essays by Lynne Rudder Baker and Peter Forrest offer materialist, naturalist account of persons compatible with Christian belief. Hud Hudson distinguishes his form of materialism from animalism. Philip Quinn's essay ‘On the intrinsic value of human persons’ provides some excellent reasons why the philosophy of mind should include a philosophy of values. In an amusing, but serious, essay, ‘Ghosts are chilly,’ W. D. Hart and Takashi Yagisawa defend dualist mind–body interaction.

Perhaps the least sympathetic treatment of dualism in the book is ‘The Word made flesh: dualism, physicalism, and the Incarnation’ by Trenton Merricks. The case against dualism is constructed largely by ignoring the ways in which dualists understand that being an embodied person involves a functional unity in which (assuming the person is healthy) to see a person acting, speaking, and so on, is to see the person him or herself. Only in cases of severe impediments as when a person is paralysed or has lost all sensory and motor control, or when a person is in the terminal stages of a debilitating illness, would a dualist think of the body as a prison or constricting container. In healthy conditions, however, there is no necessary bifurcation. Merricks's criticism of dualism seems to overlook entirely such a dualist account of embodiment. Consider this line of reasoning:

This overlooks the way in which dualists treat the embodied person as a functional unity. H. D. Lewis, the founding editor of Religious Studies, tirelessly sought to dispel such caricatures of dualism. (On this point, Merricks's position is very much like Gilbert Ryle's in The Concept of Mind; see H. D. Lewis's The Elusive Mind (London: Allen & Unwin, 1969) as a reply to Ryle and Merricks.)

As for physicalism and the incarnation, Merricks cannot be faulted for the candour of his claims:

For those with a high Christology that affirms the pre-existence of the Son to the incarnation, Merricks's proposal would involve a non-physical person becoming the very same thing as a physical thing. On a strict account of identity, this would not make sense. Merricks believes that dualists must hold that the Son becomes a human soul. But most dualists who embrace classical Christology understand the incarnation in terms of God the Son taking on (literally incarnating, becoming enfleshed) human nature, feeling, thinking, acting, and so on as the embodied being, born of Mary. This is not a matter of a non-physical reality turning into something bodily, but the assumption by the Son of human nature to form the integral reality of Jesus the Christ.

Persons: Human and Divine is highly recommended for scholars and all those interested in thinking through religious, especially theistic, themes in light of contemporary philosophy of mind.