The Discussion

The following discussion took place on the evening of the lecture, after dinner in St Edmund's College.

John Taylor: Response to Professor Murphy's paper

I would like to make a few comments. I know one or two people may not be familiar with the technical details of the philosophy of mind so I might just try and say one or two things to situate, as I understand it, what Nancey was saying to us this evening and then try and raise again one of the objections which was actually raised by Eric in questions but which I think we can explore a little further.

As I understand it, Nancey is working within a general standpoint which could be called non-reductive physicalism. I'm sure most of us are familiar with the general terminology of a dualist philosophy of mind, namely, that there's an ontological divide between the mental and the physical representing two independent substances or levels of existence. As Nancey has said, this view has traditionally been criticized on the grounds that if the mental is radically different in kind from the physical, how can the two be involved in causal interaction? There's been a lot of interest within Christian philosophy of mind in the possibility of articulating a physicalist view which could perhaps avoid some of those problems. When we turn to physicalism we can then look at more reductive or less reductive varieties, and one way in which the reductive variety has tended to be expressed is in the thought that not only are we one substance but, as it were, all our properties are of the physical kind, that is to say mental properties are in fact physical properties and states of the mind are states of the brain.

Now, a non-reductive physicalist is in some sense seeking to avoid the problems of dualism and yet not veer towards a strongly reductionist position and one way in which the intuition behind that gets going is the thought that mental properties, even though they may be properties of a physical thing, are of a different kind. One way in which that might be cashed out is in the thought that our mental life has a qualitative feel, or subjective aspect, which is distinct from the more objective third personal reality of physical properties. There is something that it's like to have a mental state (at least some mental states have that aspect). That's all very loose, and of course a lot of the interest here is in actually classifying these things. But the traditional difficulty if you want to articulate non-reductive physicalism, one of the problems that is raised for me quite acutely, as Nancey began by saying, is the question of the causal efficacy of the mental.

Materialists of the reductionist variety claim that there's no difficulty for them here because mental properties simply are physical properties and they believe physical properties are causal, in fact perhaps the only causes, so they claim that there is no real difficulty for them there. But if you're a non-reductive materialist, what are you going to say about the causal efficacy of mental properties: do you want to say that the mental can, in some sense, make an intervening difference to the physical level. If you say that it seems that you've gone down the route that the dualist goes down. Or do you want to back off and say no, in fact the mental properties, although real, are not causally efficacious, at least at the level of making a difference to what's going on in you physically. In that case, of course, it looks like you have made the mental merely an epiphenomenon. This is quite an acute dilemma which has been pushed in a different variety of contexts in philosophy of mind literature. Now, as I understood it, Nancey's response was to qualify the understanding of causality based on arguments derived from introducing an idea of a structuring cause according to which causation isn't simply a matter of trying to trigger certain events. The mental doesn't have to make pushes and pulls, or ghostly thrusts as Ryle might have called them, pushing your atoms around, but rather mental properties and mental states may be involved in some downwards causality which structures physical properties, thereby creating conditions in which the physical causes and potentialities of a brain or an organism are activated or enabled.

I suppose the question I have, which has been asked already, so maybe I just haven't really got my head round the answer yet, the question is still - do we really get round the problem, the epiphenomenal question, by introducing the distinction between structural and triggering causes? Some people might already feel that if we are saying the mental merely structures and doesn't actually trigger, then we are already on the road to epiphenomenalism, so that's one question. But if we then say that the mental properties do actually structure states of the brain, do they do that because they're mental or do they do that because they're physical? Are we going to say that there is a causal reality which mental properties can have in order to structure lower order states of the brain, and can they do that because they're mental, in which case don't we still have a sort of a problem with dualist face? Or do they really do their work, this hierarchical ordering work, because in fact they are at base physical properties and in that case, aren't we back with reductionism? So I suppose the question is now that we have distinguished triggering from structuring causes, can we not raise the epiphenomenalism objection for the structuring causes as well?

Brian Heap: Thank you very much. Nancey, do you want to come back on that?

Nancey Murphy: First, I stand by the claim of my paper that the central issue is not how the qualitative aspects of the mental have causal impact, but rather how series of events that are simultaneously mental and physical can obey the laws of reason despite their (assumed) causal connections. The concept of structuring causes was employed in order to talk about how the brain gets structured so that causal sequences realize or instantiate rational sequences. It is entirely fair to ask how the structures come to be. In my extremely simple example of learning multiplication tables the structuring is done by the environment. So the mental aspect of M2/B2 is that it is the thought of `35'. Did it not have this mental aspect, but some other or none at all, the social environment would not have reinforced its connection with M1/B1; that is, it would not play the role it does play in the environmental structuring of the brain. It is here that the mental aspect matters, but it is not that the mental aspect has any causal impact.

Brian Heap: Does anybody want to pick up on that aspect?

Patrick Richmond: Can I just query whether John's repositioning of the dilemma has really been addressed? It seems to me there's still a question of whether the mental is epiphenomenal, whether it really causes anything. Particularly I want to press the point that the mental properties with which I'm particularly concerned are the ones of which I am conscious. It seems to me that when I imagine that someone in Afghanistan is feeling great terror and pain and therefore voice worries about the bombing campaign, it is peculiarly mental properties that I'm worried about. These peculiarly mental entities, imaginings of terror and pain, are doing the work. The mental images explain my behaviour. Likewise, when I plan how I'm going to fit all the plugs into my computer I might visualize doing so. It is my visual imagery that helps me sort out how to put the plugs in. The mental image, not just the state of my brain, appears to cause the physical action. It is just these mental causes that are at risk with physicalism. How does the mental, and not just the physical correlated with it, cause anything? It seemed to me, Nancey, that a problem with what you were doing in your lecture was, like many politicians, you decided that the important question wasn't quite the one that Kim asked, about how the mental causes things. You rephrased it and you answered your own question, but I still felt that a real issue covered by Kim's original question hasn't really been addressed: How do my intentions, my felt drives, my raw passions cause anything? Instead, you've offered us a non-reductive and helpful account of how reason and rationality could shape my brain processes. However, it's left out just what I wanted addressed, the fact that the mental feels like something. Robots, zombies or an alien race of walking calculators might be in some sense logical or rational, but they wouldn't feel anything.

Nancey Murphy: All I really intended to do tonight is to work on one tiny piece of the puzzle, how can you reconcile rationality with causality. You've asked the big question about consciousness, which I don't attempt to deal with. I think it's got to be left for farther down the road when we know more about how the brain works. I am convinced, as a physicalist, that somehow or other the activity of our brains gives rise to consciousness, but I'm not at all sure that we'll ever have much subjective sense of understanding how that happens. But when you talk about the mental you're actually throwing together a whole ragbag full of different kinds of conscious events: feelings, imaginations of future events, along with a rational calculation. All of those are important and they're on the agenda for later.

But I will just say that I think that imagination plays a huge role in our rational capacities because when we get beyond the point of just answering questions about the multiplication tables or some simplistic things like that, much of what distinguishes human mental capacity is in fact our ability to imagine future scenarios and the causal connections leading up to them; I'm sure that that's going to play a huge role in understanding the extent to which we are free beings, rather than merely automatons that can calculate almost as well as calculators. So all those questions are extremely important ones; they've got to be worked on in the future but the fact that I can't answer them now does not detract from the validity of the tiny little first piece that I've done.

Brian Heap: Would anybody like to pick up this issue of `bottom up' and `top down' which worried me.

Denis Alexander: I'm not sure it picks up quite that point, but I did want to make a point as a lapsed neurochemist who in past years was much influenced by the writings of the late Donald MacKay. One aspect of MacKay's thought which I found helpful was his insistence on a linguistic hygiene in which the internalist account of our own subjective experience - represented by `I language' - was kept distinct from the `it language' of brain descriptions made by scientists which of course represent the mental correlates of the `I language'. MacKay maintained that both accounts are complementary in the sense that they are accounts of identical events but made from the standpoint of very different perspectives - the `internalist' and the `externalist'. So the two accounts are like the two sides of the same coin, but if we try to mix the two languages then this inevitably ends in confusion. This touches on some of the questions that have already been put this evening - in practice how is it that the `fusion' between the two accounts occurs? I think MacKay's point was that we have here a genuine ambiguity. We must do justice to our experience of other peoples' brains as neuroscientists - the `it language' - and at the same time we must do justice to our own world of subjective experience and mental events - `mentalese' is no mere epiphenomenonon of our physical brain states. So we end up with two language sets. These are not dualistic in the sense that John was just outlining but represent what MacKay dubbed `dual-aspect monism'. As a scientist I very much identify with this position because it enables one to do serious brain science and to go as far as you can in describing all the physical events but at the same time maintaining linguistic hygiene in giving primacy to the conscious experience.

Now I can see the danger in complementarity is that you can separate out those two perspectives too much and I think McKay was very aware of that, and would always emphasise the tight linkage between the `internalist' and the `externalist' accounts. But I suspect as a philosopher that you may find this approach a cop-out.

Nancey Murphy: It is a copout. As a scientist, let's say, you can flip a coin and you can only see the tails side, but you've got good reasons in terms of physics and statistics to know how it's going to come out. How can the head side come out any different from that? So you can, by linguistic convention, decide that the philosopher at the table can only talk about the head side, and you as a scientist can only talk about the tail side, but we know they're connected.

Denis Alexander: Yes, clearly they are tightly connected, but I think MacKay's point was that we should do full justice to both complex sets of data even if we cannot for the moment see how they can be integrated. Living with such tensions often happens in science. The classic example was the wave theory of light contrasted with the corpuscular theory of light. Sometimes light behaves like waves and sometimes it behaves like particles - both models are required to do justice to the data collected on the properties of light, even though conceptually the two models conjure up rather different images. With time a better model comes along (quantum theory in this case) which manages to integrate the data in a more satisfactory way. It seems to me that in science it's quite common to live with two sets of data even though it's not always easy to see how they fit together. Non-reductive physicalism currently has to live with this kind of position in giving equal weight to `internalist' and `externalist' accounts of human experience without really understanding how one `translates' into the other.

Nancey Murphy: It's right that you shouldn't mix elements of the two languages in a careless manner. A friend of mine has just published an excellent book in which she criticizes the way neuroscientists and their interpreters weave together psychoanalytic accounts and common-sense observations of human behaviour with very basic neuroscience, and then claim that they've explained one in virtue of the other, when actually there are many layers of complex connections in between. [Leslie Brothers, Mistaken Identity: The Mind-Brain Problem Reconsidered, SUNY Press, 2001]. So I appreciate MacKay saying not to mix the language of free will, consciousness, human determination, etc. with the neuroscience language. But having said that, Donald MacKay of all people should know that if you're a physicalist everything that we talk about at the consciousness level must have a neurobiological correlate of some sort and there is causation at the neurobiological level.

Fraser Watts: I wonder if I can come in on this dual aspect monism - I never know quite where I stand on these issues, but some days at least I think I'm a dualist. And if you are, then I think it's perhaps misleading to even begin talking about mental events, or brain events, because I assume that there are no brain events that are unconnected to mind and no mental events that are unconnected to brain and if these are just two faces of the same reality, to set up the problem in terms of mental events and brain events is to set it up using misleading terminology.

Nancey Murphy: Yes, and the problem is that we inherit our terminology from 2,500 years of history in that we have these conventional classifications of certain happenings as mental and other happenings as physical. But how do we talk about the relationship between those two kinds of things without talking about the mental and the physical? Maybe that's what Paul and Patricia Churchland are up to with their eliminative materialism; maybe they're hoping to wipe out one half of the vocabulary, or replace half of the vocabulary. But we just can't.

Fraser Watts: Well you perhaps have to recognize that you can't use one language without the other, and if you try then you are misleading yourself.

Nancey Murphey: One point where I would take issue is your claim that every neurobiological event has a mental aspect to it. I think that a whole lot goes on in the brain that we're completely unconscious of. But I would assent to the contrary--that every mental event of course has a neurobiological correlate or set of correlates.

John Taylor: There might be issues here about whether or not the vocabulary of events is the right terminology. We have all of these terms, we have states, we have processes, we have conditions, we have events, we have a whole lot of possible different structures or linguistic forms, or if you want to be metaphysical, entities here, and of course they might well behave differently within the two different realms and of course they may not match up very nicely. This is a point I know some Oxford philosophers of mind pushed against Davidson. We don't carve up the mental terrain in the way that we carve up the physical terrain. And that must create questions about the definition of supervenience which usually is cast in terms of events.

Nancey Murphy: At the mental level we've got states, the continuing state of believing, events - I suddenly remembered that I forgot my gloves - and processes, I'm trying to do some sort of calculation, but at the neurobiological level, isn't it the case that it's mostly processes, active processes but states in terms of structures.

Patrick Richmond: But there are significant neural events. When someone starts to think about moving their finger, you suddenly get excitation of the pre-motor cortex, or, if Karl Popper and John Eccles are to be believed (In their The Self And Its Brain), there are sudden eruptions of cortical activity that have no obvious cause but lead to motor events.

Nancey Murphy: That seems right. So maybe what we want to say is that what is a state at the mental level could be a process of the neurobiological level, that there isn't any correlation among states, events and processes at the two different levels.

John Taylor: And you might even go more general - people like Ryle and others who made a great play of the fact that a lot of our mental vocabulary is not concerned with actualized entities but with potentialities and dispositions. If we're going to talk about reason rather than cause, then being rational is perhaps partly a matter of having certain dispositions and certain tendencies and then the relationship becomes even less clearly discrete and nicely carve-up-able. In one sense you don't have an entity at all, you have a trait, something which can be realized by a process but which isn't itself a process.

Brian Heap: Gerry, do you want to come in at this point, shall we just move to a slightly different tack?

Gerry Gleeson: Perhaps I can raise similar issues from a different perspective. Nancey, in terms of your overall project, you didn't elaborate on how you understand the concept of supervenience. I don't know if you can be expected to do that now - but I'm wondering whether you can pass over this point so quickly because it does seem to be critical to the debates about mental causation. The debates are precisely about how supervenience is to be understood. In some of the discussions in this area people take supervenience as unproblematic, whereas I take Jaegwon Kim's point to be that it is very difficult to combine the supervenience of the mental with its causal efficacy. That is why I wonder if you can pass so quickly over this issue.

The other issue I would like to raise concerns who is the subject of all this mental activity. Your argument sought to reconcile rationality with causality, my question is who is being rational here? Does the fact that there is a structural association of ideas in the brain (e.g. between `5 x 7' and `35'), really amount to a person's being rational? It seems to me that this sort of association could well be set up neurologically by rote learning (e.g. because when I was 7 years old I was made to chant out `5 sevens are 35'), but this seems to me to be not an example of rational thought at all, but exactly the sort of thing that might be explained by a pairing of neurological items. So I wonder whether your proposal is really getting us to what it is for a person to act rationally. We may be talking about brains that have managed to be hard- or soft-wired in certain directions but are we really talking about people?

Nancey Murphey: First of all, on supervenience, the mainstream interpretation is in terms of property co-variation and the only difference between identity and supervenience is the concept of multiple realisibility.

Brian Heap: I think some of us have not followed that. Could we have some clarification of terms for those scientists round the table who are not familiar with them. Please could you clarify `supervenience' so that we can stay with the discussion.

Nancey Murphy: Because the definitions are so highly contested, I think that the best way to convey the notion is by an example. It's a way of relating properties or characteristics or events and, I would say, such that a lower level state of affairs constitutes the higher level state of affairs. The original example was R. M. Hare's description of the relationship between moral properties and non-moral properties. St. Francis' property of being a good person supervenes on a collection of non-moral properties such as giving his money to the poor, chastity, etc. The notion of multiple realisibility is simply to say that there are lots of ways of being a good person other than St. Francis'. In the technical literature, Jaegwon Kim is probably the most influential. He attempts to define supervenience in terms of property co-variation, so that if there is a difference in the supervenient level there must be some difference in the subvenient level as well, but not the reverse. That is, you can have the same supervenient characteristics, such as being a good person, but with a variety of subvenient sets of characteristics, such as those of John Bunyan or those of St. Francis.

Now the point where I disagree with Kim is that he doesn't take into consideration the fact that the same lower level qualities can either result in goodness or not goodness depending on the circumstances; so for instance if St. Francis is a married man with children to support, then his celibacy and giving away of all of his goods to the poor would not constitute him a good man; it would constitute him a bad husband and an irresponsible father. So I think that the supervenience literature needs to go off in a different direction to talk about the lower-level qualities as constituting the higher level supervenient qualities, but only under given circumstances. This is very important in the philosophy of mind because it pays attention to what philosophers of mind call externalism; that is, to have the same brain state isn't necessarily to have the same mental state unless much of the environment that the mental state is supposed to be about is the same. So the issue of how you define supervenience is important; I just didn't need to get into it for the purposes of this particular paper.

Gerry Gleeson: Except that, I suppose, this takes us back to the question I asked at the lecture, namely about the connection between one's thought of grandma and what's happening in one's head. That's the big question here, namely about the content of the thought.

Nancey Murphy: Suppose our brains are perfectly isomorphic, and you have a brain state that is exactly the brain state I have when I think of my grandmother. Then you're not thinking of your grandmother, you're thinking of my grandmother, and so its the context that makes the difference as to whether you're thinking of your grandmother or mine. That's the sort of thing that one needs to make room for in the definitions of supervenience; as long as you set out to do it in terms of property co-variation you're not going to have any way of incorporating this essential ingredient into the concept. The way I use the term is much more in line with the original use in ethics.

Gerry Gleeson: I've also got a worry about whether the ethical model of supervenience which sounds really plausible in the case of the St. Francis example, really works when you start to talk about the mind-body relation. This seems to me to be a much more difficult area.

Nancey Murphy: The supervenience relation in the area of morality is different, depending on your meta-ethics. If you're a utilitarian then it's a sort of factual relationship: such and such behaviour at the subvenient level constitutes goodness at the supervenient level because of facts of the matter about the kind of consequences it has. If you've got some other moral theory, deontological or divine command or whatever, the supervenient description of goodness relates to the subvenient behaviour or character traits for different reasons, so there are all sorts of ways in which higher level properties can supervene on lower level properties. So first we need to lay out those possibilities and then start thinking which, if any, is the sort of relationship that best models mind-brain relations. Probably we have to solve the small and nagging problem of the nature of consciousness before we can settle that issue, so we're a long ways off.

Now with regard to the question of who's the subject of mental activity, I have just written a chapter for my current writing project with Warren Brown on various ways of being a Cartesian materialist and one of the ways is by making neural events the subject of the activity. We've got to hold out very strongly in a sort of Wittgenstinian way, saying that the whole system is the subject; when I do something it's the whole person, not just the brain and certainly not just a few neural events, but the whole of me - mouth, ears, feet, etc. -- that is the subject of my rational activity. This is hard to do because we rather naturally become Cartesian materialists -- we're used to thinking of the real `I' as the homunculus inside the mind. It's very hard not to think of the real `I' as a set of events going on inside the brain.

Gerry Gleeson: And you're not worried that your account is heading in that direction?

Nancey Murphy: Well, I think it's something that I have to lean hard against doing. I feel like I've always got to be watching myself

Gerry Gleeson: Because what I heard us talk about tonight was not a person, but a brain that spat out 35 when someone fed in seven times five.

Nancey Murphy: Oh, the operating system is in here, but the effector includes the mouth talking, so the feedback is meant to include most of the physical organism, anyway. Ears, hands, mouth.

Gerry Gleeson: This sounds rather like a redefinition of the problem.

Patrick Richmond: May I just chuck in an anecdote from my medical days? We were having a seminar with the neuroscientists, and were shown a diagram of the brain. It was fairly boring stuff about visual stimuli. On the diagram were some other inputs from the five senses and also a bit about emotions, limbic systems and things like that. So I, feeling a bit bored, said, `I have this sense of being an `I', who actually determines things, who takes into account what I'm feeling, and makes decisions based on that. Where does all that happen? Is it the pineal gland?!? And the neuroscientist said `No' and pointed out various tracts within the brain seemingly feeding to what I think was the prefrontal cortical area. Here was a place that had inputs and outputs that were reaching round the brain - so the idea that there might be some sort of central command centre was not alien to the neurophysiology that was being done six years ago.

Edwin Chilvers: This is very complicated but perhaps I can contribute in this way. I have no doubt that through advances in neuroanatomy, and functional imaging in particular, that more of the brain will be `mapped'. It is highly likely that this process will `peg down' many non-physical attributes to a particular brain region. But it's a question of how far that process will or can go and how much of our personality and thought processes and spiritual awareness will be physically mappable; I think this will be very interesting. I could come at this as a Christian; the Bible talks very clearly about an individual being composed of a body (with a mind), a soul and a spirit, all of which serve distinct functions. I regard these as important, independent players that make up a spiritual being. My personal view is that the divide between the organic, `mapable' bit and that which operates without such physical boundaries will be between the mind and the spirit not between the body and the mind.

Brian Heap: This was one area that troubled me but from a very different angle. It's an experience that Derek Burke would have had also where in the scientific field the view has existed that an invention or a discovery leads to a development, which then leads to an application, which then leads to becoming a millionaire, or whatever - the linear model. There is certainly a difficulty in perceiving the brain in terms of `top down' or `bottom up' because modern neurobiology and in particular functional magnetic resonance studies show a huge interaction across many brain regions. The whole concept has now shifted to one where a massive interaction is observed between many components and centers.

Patrick Richmond: Strip away the cortex and see how far you get!

Nancey Murphy: The philosopher Daniel Dennett is highly critical of the notion of the Cartesian theatre transferred to brain science. He and the neuroscientists that he works with claim that there just isn't any place where it all comes together. Notice that it's one thing to ask whether there is a part of the brain that does it -- that is, creates a sense of self -- and it's another thing to ask whether there is a part of the brain without which you can't do it. Remove the neocortex and of course you don't have any sense of `I'. But that doesn't mean that the neocortex alone or any particular part of it gives you the sense of `I'.

I was talking with Frank Carey earlier today about Karl Rahner's theology, in which the notion of self-transcendence plays a large role; in fact Rahner defines spirit as self-transcendence. I believe that the notion of self-transcendence is extremely important for understanding how we avoid neurobiological determinism. Because we've got the capacity to think reflexively, to reflect on our own mental capacities and our own emotional processes, we're able to raise the question about ourselves, at any particular moment, of whether our behaviour or thoughts are determined either socially or biologically. In the diagram I used in my paper, this is an instance of adding a higher-level supervisory system to whatever system you've already got in place.

Once you raise the question `is my current behaviour or thinking determined by something by which I don't want it to be determined?', you thereby free yourself from that determinism (unless it's an addiction or something like that). An interesting grammatical fact is that whenever we make such a move, we associate the nominative pronoun `I' with the highest level supervisory system and call the rest of the system whatever it involves `me'. So, for example, I am now conscious of the fact that I am talking to you about these things and now I'm conscious of the fact that that I'm conscious of the fact that I'm talking to you about these things, etc. I suspect that this capacity has a lot to do with our sense of `I' and the reason that the `I' seems so elusive whenever we turn our attention to it - it has just made a transcendent leap and now it's thinking about what used to be the `I'.

Eric Olson: Do you really think that there are all these different thinking things acting when you think and that - now one was thinking and now the next one's thinking. Did I misunderstand?

Nancey Murphy: Not different things, but we have to understand our mental processes hierarchically and if so then, on the physicalist assumption, there are neurobiological realizations of those abilities to transcend thinking processes.

Brian Heap: Is that really true? Do we have to think of them hierarchically?

Nancey Murphy: Not the brain itself, but you just have to say somehow or another the brain provides the capacity to turn our thinking processes on our thinking processes; this probably requires a certain level of linguistic sophistication.

Fraser Watts: This is a rather different kind of question, if I may. I want to ask about God in all this. Well I assume that minds and brains exist in some sense within the life of God and I assume that God is, how does one put this, at least in part a transcendent being - and does that make any difference at all to the mind-brain problem? I got the impression from the answer you gave to Patrick at the start of the questions you thought it didn't make any difference at all and, if that's so, that seems to me surprising, but perhaps I can try and draw you out a bit on this.

Nancey Murphy: Well, I don't think our understanding of God's relationship to the world solves the immaterial mind-body interaction problem.

Fraser Watts: It contextualises it?

Nancey Murphy: It has in the past. I just don't see that it helps.

Patrick Richmond: I apologise for originally phrasing the question badly, because what I was actually seeking to do was invoke a bit of humility amongst philosophers and remind them that at least since Hume we've realized that we haven't got a good grasp of physical causation, physical-mental, mental-physical and that when God is brought in we're all humbled. So I phrased the question wrongly. I didn't want to say because we understand the way God controls the world, therefore we understand the way the immaterial soul does. I wanted to say `come one, let's be humble' - if this is a decisive attack on dualism it's a decisive attack on western philosophy, it's a decisive attack on most forms of metaphysics.

Nancey Murphy: Which was the point of my reply, that I see the problem of God's interaction with the world as the chief theological problem, but re-introducing souls does not solve that problem either, it just adds to it. It adds a whole bunch of little problems.

Patrick Richmond: No, but you've rejected the soul on the basis of our lack of understanding, but are hanging onto God despite our lack of understanding.

Nancey Murphy: Well, theologically we've got to. However, there is no adequate theological reason to hang on to dualism, according to my reading of the biblical texts and my scanty knowledge of Christian history.

Patrick Richmond: Right, well I think then we've interacted; we have clarified the real reason why you have rejected traditional dualist accounts of soul and body.

Fraser Watts: But it still seems to me surprising if the existence of a transcendent God makes no difference whatsoever to how one approaches my brain relations.

Nancey Murphy: Tell me how it should.

Fraser Watts: Well, because mind and brain are part of a larger reality who is God, and that reality is different in the sense of being transcendent. Even though many people might see mind as emergent from brain, one's not going to see God as kind of emergent from the physical stuff of the universe in that kind of way, so there is something transcendent which is prior and so any self-transcendence which occurs in the human mind is occurring in the context of a transcendent God. I would have thought that that sort of context affects how it functions, how it operates.

Nancey Murphy: Oh I certainly think that human thinking is affected by God but I think of it in terms of, to put it crudely, God having to do with human brains. I realize that I'm out of step with about 1500 or 1600 years of Christian history in claiming that it does not require any intermediary of a soul or a mind in order for God to be able to affect us.

Fraser Watts: I'm not postulating a sort of rarefied soul but I really wouldn't think that God has to do with brains. I would think that God has to do with people, actually and mind-brain unities.

Nancey Murphy: There I've done it. I've just slipped into Cartesian materialism again.

Brian Heap: There are several others who want to comment. Janet?

Janet Soskice: If you bring God into this, one of the things that seems important in Christian history, in the history of theology, is the hammering out of Christian orthodoxy against various heretical and what become heretical alternatives. In particular the consensus that God creates everything. The body is a creature but the soul is also a creature; and the spirit, too. Every aspect of our reality is created reality, and the big contrast in theology is not between mind, spirit and body but between what ís created and the One who creates, that ís the fundamental distinction and it ís far more absolute than `things that go bump in the night'.

What early theologians had to contend with was various kinds of neoplatonists who did argue for an immortal soul and indeed which participated in the divine - a chip off the divine block. Christianity and Judaism did not believe that because they believed that the human being was totally a creature, although destined for sharing the life of God. The creature could get caught up into the life of God, every aspect of it. It is not as though the mental aspect of it, or the spiritual aspect is any more godly, any more worthy, than the material, and in this sense I don't know whether the history of Christian theology is so out of step with what you are saying. I think you could make a perfectly plausible case that what you are saying is what historical Christian theology has already said. But you need to emphasise creation: spirit is created, soul is created, body is created; in one sense you could say they are all material realities, that would be a direction you could take and be consonant with historical Christianity.

Nancey Murphy: I think that adopting physicalism is a very healthy thing for Christians because it establishes the ontological dividing point just where it should be, which is between God and everything else, rather than half way up the great chain of being.

Janet Soskice: Some of the dualism seems frankly more like agnosticism and neoplatonism than Christian orthodoxy. I know some lovely people who are very interested in the spirit world and that fringe of the science/religion debate where people become interested in paranormal experience but I think, again in terms of historical theology, that the divide between the spiritual and the material is not the divide that mattered in historical theology. The divide that mattered was between the created and creatures.

Frank Carey: I think the only occasion when I find it necessary to say I'm a Catholic priest is when I know I'm going to say something really dumb. I would say that with a lot of the debate, I can't follow it with the intricacy that others can, so I come to it from a different perspective. When we're talking about God, the only thing we know for sure about him is what he is not. If we're talking about God as a determinate being, somehow it's an idol, a false image of God. There's one thing that I haven't noticed in the discussion, and this is where I feel I'm being really dumb, so I should explain the perspective that I come from with, hopefully, the majority of humankind who are struggling and very very poor. I don't really have the vocabulary to express properly mental states and physical states, but if we're talking about the kind of love that sustains a woman in Africa who has Aids who is struggling to support her kids, how do we speak about, in this context, people who use a dualistic vocabulary? They will even engage in dualistic activities, spirit worlds and this kind of thing, but it keeps their nose above the water, otherwise they would sink. So how are these things like fortitude, courage and lifelong dedication, related to brain activity, that kind of thing? It's these kinds of lifelong commitments that keep people going against the odds. Is it a dumb question?

Nancey Murphy: No, it's not, and it focuses quite nicely on the distinction between reductive and non-reductive physicalism. The non-reductive physicalist is committed to recognizing the existence of those human characteristics and saying that the interesting thing is to figure out what's going on in our bodies that allows us to sustain them. I'm also very interested in the continuities between goodness in animals and goodness in us. However, we can't have the kind of moral goodness that we've got without linguistic capacities.

Colin Humphreys: I have a simple question: I am a materials scientist, and my understanding of physiology is extremely limited. My question concerns the difference between physical and mental. If you have two identical twins then presumably you say they are identical physically but can be different mentally, so if you go and look into their brains, do identical twins have the identical number of brain cells, do they have similar links between cells, do they have the same number of folds in their brains? I presume identical twins have the same number of brain cells and similar links between them at birth, but I may be wrong. If the links between brain cells are different then do you call that a physical difference or a mental difference, presumably it is a physical difference. So if you have two identical twins, then what do we mean by the difference in their mental states?

Nancey Murphy: There are other people who could answer the physiological questions better than I can. My understanding is that there is not enough information in the genome to determine the wiring of the brain and so much of the way the brain turns out is a matter of random growth. Then there is the reinforcement, or lack of reinforcement, that comes from environmental experiences and probably even in utero there are enough differences in experience that by the time identical twins are born their brains would be somewhat different. Then insofar as they each experience different things after they're born, their brains get more and more different.

Brian Heap: As an example of your point, Paul Ehrlich (2000) in Human Natures relates the case of Chang and Eng who were Siamese twins born on 11 May 1811. They were genetically identical joined at the base of their chests and it was not possible to separate them. As they grew up it became obvious that there were striking differences in their behaviour. Chang was the dominant brother and quick-tempered. Eng, in contrast, was agreeable and usually submissive. Chang drank to excess and Eng did not. In old age, Chang became hard of hearing in both ears, but Eng became deaf only in the ear closer to Chang. In the summer of 1870 Chang suffered a stroke that left Eng unaffected but bound physically to an invalid. When Eng discovered his twin's death, although perfectly healthy he became terrified, lapsed into a stupor and died two hours later. The case shows us that genetic identity does not necessarily produce identical brains and identical natures even when combined in substantially identical environments - in this case only inches apart with no sign that their mother or others treated them differently as they grew up. Genetic instructions, therefore, are of great importance, but they are not our destiny.

Jonael you look as if you are poised to speak.

Jonael Schickler: I'm unhappy with a lot of things that have been discussed and would want to move the goalposts probably too far for it to be worth it at this stage. I would, though, say the following. The concept of the mental that has been discussed has been focused on the sensory component of our mental lives. Equally fundamental to a satisfactory conception is an irreducibly intelligible component. The distinction between the sensory and the intelligible is fundamental in the philosophical tradition from Plato and Aristotle right through to Kant and others, but it is ignored by the physicalist. Kant, for example, shows how the very notion of an object, which is taken for granted by the physicalist, depends upon a priori ordering capacities (which belong to what he calls the understanding), in order to be conceivable as an object in the first place. In the process whereby we come to have experience of objects, the understanding interacts with what Kant calls sensibility which provides the sensory component of the experienced object. (There are, of course, many questions about how this interaction takes place, but this would take us into a more technical discussion.) In our discussion so far, however, it is the sensory component alone which has been identified with the mental. The question has been: how do material objects (e.g. the brain, sense organs etc.) cause sensory experience? From the Kantian (or indeed Aristotelian) perspective, this very question is misconceived, since a material object is itself an object of sense experience to which order and unity has already been given by conceptual categories so it cannot be conceived as existing mind-independently. Indeed if we take this basic starting point, all knowledge of nature must be subject to the way our concepts order the perceptual world. So the first question to ask is not: how is the physical world related to the mental?, but rather: how do our concepts and percepts - the two main so-called mental sources of our experience - interact to give us experience of an object? Kant himself thought that we could not understand the relation between them, which is what makes his philosophy into a skeptical one. However, he obviously realized that there must be a relation between what e.g. goes on in the brain and what we experience in consciousness. He thought this relation to be unknowable because for him knowledge of nature is limited to the mechanical means of understanding it (which itself, of course, already depends upon the mind). To know higher levels of being (such as those responsible for consciousness) the mechanical form of understanding which analyzes nature into basic constituents would have to be overcome, which he considered impossible. For him we cannot even know the formative forces intrinsic to living organisms, let alone the true origins of sentience or thought.

The bottom line, then is that modern scientific knowledge of how brains function etc. presupposes rather than explains thinking. As knowers we engage in two main activities, perceiving and thinking. It is the result of these activities that gives us knowledge of nature. Correlations can certainly be made between events observed by the scientist and our experiences, but there are no philosophical grounds for turning these correlations into causal relations. .If further levels of being were discovered - levels corresponding to life and sentience, for example - then the possibility of turning these correlations into causal relations might be realized. Then it might become possible to explain what, for example, happens when we fall asleep and cease to be sentient i.e. what happens when the level of being intrinsic to sentience separates from the physical body. However, this aim is very far from having been realized in modern science.

I would personally, following Aristotle, Aquinas and more recently Steiner, defend a basic four-fold conception of the mind-body relation (separating the physical, living, sentient and thinking). This, if it could be properly developed, would help us to overcome both Kant's skepticism and to provide a non-dualist anti-reductionist conception of the mind-body relation.

So you see for me the whole debate has so far simply assumed that one can unproblematically refer to a mind-independent physical world. Since Kant it has been clear that this world is itself an object of experience given structure by the basic categories of thought. We never, in short, leave the realm of the mind or the mental. The material world of natural science is simply one sphere in which it is active. This does not mean that there is not a world that exists independently of it, but simply that much more would have to be known (i.e. the different levels of being that I have distinguished) for it to be accessible to us.

Leaving aside Kant and a means of overcoming his skepticism, the most important omission for me in our discussion has been a clear distinction between the sensory and the intelligible as the basic starting point in the philosophy of mind.

Nancey Murphy: Well, I would want to leave Kant aside. I obviously don't think in Kantian terms, and couldn't briefly explain why I object to Kant's conception of knowledge. I would point out, though, that the discussion has not been limited to sensory experience. We have talked about arithmetic and the concept of self, two topics of interest to Kant.

The point at which we can agree, despite our differences, is on the importance of understanding how concepts are formed and how they affect experience. This raises all the questions about the extent to which we are genetically predisposed to develop conceptually in particular ways. I recently read George Lakoff and Mark Johnson's book Philosophy in the Flesh (Basic Books, 1999), in which they argue that much of our conceptual scheme is built up by metaphorical extension of concepts developed in the course of basic physical activity. For example, the concept of a category is based on our experience of putting things in containers.

Brian Heap: Well, thank you very much indeed. I think that's been a very valuable discussion which will go on into the night. Thank you to all who have contributed.

Discussion participants

Prof. Nancey Murphy, Professor of Christian Philosophy, Fuller Theological Seminary, California, USA. Specialised in philosophy of science and religion.

Sir Brian Heap FRS, Master, Vice-President Royal Society, reproductive biologist, Department of Health Expert Group on Cloning, Nuffield Council on Bioethics.

Revd. Dr Patrick Richmond, Chaplain, St. Catharine’s College. DPhil in Cell Physiology before ordination. Interests in philosophical theology and ethics.

Professor Colin Humphreys FREng, Goldsmiths’ Professor of Materials Science, Selwyn College, formerly President of Christians in Science, has written extensively on questions of Biblical dating.

Dr. Fraser Watts, Starbridge Lecturer in Theology and the Natural Sciences. Fellow and Director of Studies, Queens' College.

Dr. Jonathan Doye, Royal Society Fellow, Department of Chemistry.

Dr. Paul Shellard, Cosmologist, Dept. Applied Mathematics and Theoretical Physics.

Prof. Edwin Chilvers, Professor of Respiratory Medicine, Department of Medicine.

Dr. Terry McLaughlin, University Senior Lecturer in Education, specialises in philosophy of Education.

Rev Dr Gerald Gleeson, Visiting Scholar St Edmund's College, Senior Lecturer in Philosophy, Catholic Institute of Sydney, and researcher into medical ethics

Dr. Janet Soskice, Reader in Philosophical Theology. Fellow and Director of Studies, Jesus College

Dr. Eric Olson, University Lecturer in the Cambridge Faculty of Philosophy and a fellow at Churchill College.

Prof. Derek Burke CBE, Honorary fellow, molecular biologist, formerly Vice-Chancellor, University of East Anglia.

Dr. John Taylor, philosophy teacher, Rugby School, and Centre for Cultural Studies, Regents Park College, Oxford.

Mr Daniel Johnstone, President of St. Edmund’s College Combination Room, studying the philosophy of religion.

Dr. Denis Alexander, Fellow of St. Edmund’s College, Chairman of the Molecular Immunology Programme, The Babraham Institute, Editor of Science & Christian Belief.

Mr Jonael Schickler, Director of Studies in Philosophy, Hughes Hall College, and postgraduate student at Queens' College, Cambridge.