Philosophy of Mind: 00-01
MIND-BODY DUALISM
What is Dualism?
There are several general ways of answering the questions “What is mind?” “How is mind related to the rest of the world?”:
We will be looking here at dualism, which is by far the most appealing of the alternatives to physicalism. There are two reasons for the appeal of dualism. First, idealism and panpsychism are implausible: it is hard to believe that matter does not exist, and it is hard to believe that simple physical things – such as atoms or rocks – have mental aspects (such as simple experiences). Second, many find the idea that they themselves could survive the annihilation of their bodies – or even the annihilation of the physical world as a whole - very plausible (or at least desirable), a possibility which presupposes that we ourselves are non-physical entities.
Varieties of Dualism
Dualism comes in many flavours; we can start by distinguishing three main varieties:
· weak or materialist dualism: we are not immaterial beings, but we are substances that are distinct from our bodies or brains, because we have different persistence conditions (see Lowe chapter 2)
· traditional substance dualism: there exist immaterial (i.e. non-physical) mental things - minds - and all mental states (beliefs, experiences) are states of such things; since we have mental states, we are ourselves immaterial beings, who happen to be in contact with material bodies
· cosmological dualism: let “the cosmos” mean “the totality of everything which exists”; the cosmos includes two separate and entirely different universes, one physical, one mental, and these interact (see McGinn’s “Hyperdualism Ventilated”)
We’ll be focusing on traditional substance dualism, although I’ll mention Lowe’s weak dualism briefly at the end.
Questions of substance and bundle: it’s common in the literature to distinguish “substance dualism” from “bundle-dualism” (or “property-dualism”). The basic idea is this: whereas the substance dualist (such as Descartes) says that minds are non-physical substances, i.e. genuine entities, which possess mental properties and states, the bundle dualist denies this, and maintains that only mental property (instances) and states exist – the substance doesn’t. I
It’s not entirely clear that there is a real issue here, for there are two different metaphysical accounts of what an object is: there are those who say an object consists of a two sorts of item: a substrate and properties, there are others (“bundle theorists”) who say that an object is just a collection of properties which are unified by a special property-unifying relationship. Bundle theorists don’t deny that objects (or substances) exist, they simply have a different account of what objects are – they deny the additional “substrate” entity. Consequently, bundle dualists can insist that minds exist – as genuine objects, composed entirely of mental states/properties.(1)
Questions of interaction: this is a more significant issue. Let’s suppose that the mind is an immaterial entity. We now ask how minds are related to the physical world. There are two popular possiblities:
· INTERACTIONIST DUALISM: minds and bodies causally interact; bodily events cause mental events - e.g. damage to your toe [physical] causes you to feel pain [mental] - and mental events cause physical events – e.g. you decide to put up your hand [mental] and your arm rises [physical]
· EPIPHENOMENALIST DUALISM: physical events can cause mental events to occur, but mental events cannot causally influence physical events; the mind is a causally impotent “epiphenomenon”.
· PARALLELISM: there is no causal interaction between minds and bodies, but things are so organized that mental and physical events run in parallel, and it seems as though they must be interacting, even though they aren’t.
In practice, only people who believe in God take parallelism seriously. Let’s move on to consider the case for dualism of the traditional sort: i.e. the claim that there are both immaterial minds and a physical world.
For Dualism
There are many bad arguments for dualism (see Lowe chapter 2), but there are also some which have to be taken seriously. Here are two such.
(1) Failure of Physicalist Accounts of Mind
Over the past few weeks we have seen that all the standard physicalist accounts of mind are problematic: behaviourism, identity theory, functionalism. The overall lesson is this: (i) there are some mental attributes (e.g. the ability to do certain things, such as play chess, or remember sequences of letters) which we can easily envisage physical things as possessing (e.g. computers), (ii) but the problem of consciousness remains unsolved: it is very hard to see how anything entirely material could also have experiences. The identity theory and functionalism have serious problems here:
So the dualist can argue in this general way:
This is clearly an argument that has to be taken seriously. However, even physicalists who accept that current physical accounts of mind are flawed are not obliged to embrace dualism. There are several responses they can make to the argument, e.g.
“OK, we’re not there yet, but so what? We are making progress, and we believe that we will come up with an adequate materialist account of the mind, the conscious mind included. There are two main reasons for thinking this likely. First, the life analogy: science has already solved many seemingly insoluble problems, such as accounting for living things in wholly physical terms. Second, dualism itself suffers from serious problems. Putting these points together, it is reasonable to reject dualism.”
This reply has some force – or rather, it would have if dualism did suffer from very serious difficulties of its own. We’ll be looking at these alleged difficulties shortly.
(2) Imaginability
Here’s a quick run-through of the basic argument:
Here (of course) “identical” means one and the same thing as rather than has the same properties as (i.e. it is the concept of numerical rather than qualitative identity that is being talked about).
A rather more formal way of stating the argument runs thus:
(6) From (1) it follows that my mind and body are not identical at all.
The first premise has considerable plausibility. If “x” and “y” are names of the same thing (e.g. “Clark Kent” and “Superman”), it is hard to see how the entity referred to by “x” could exist in the absence of the entity referred to by “y” – after all, these names refer to one and the same thing – in this case, a certain individual from the planet Krypton. So if “x” is my mind, and “y” is my body, it is reasonable to suppose that if it is genuinely possible for x to exist in the absence of y, then my mind must be an entity in its own right that is numerically distinct from the entity that is my body (or brain).
Premise (3) is also very plausible: it is easy to imagine one’s mind existing in the absence of one’s body. E.g. I can easily imagine that the physical world is an illusion produced in my mind by an Evil Demon; I can easily imagine continuing to exist as a disembodied point of view after my body is destroyed in a fire.
The crux of the issue is premise (2): is it really true that “what is clearly imaginable is logically possible”?
In a sense, the answer has to be “yes”. The notion of “logical possibility” is very broad: everything that is not inherently contradictory is logically possible. A round square is not logically possible, but a flying pig is (the latter is nomologically impossible, i.e. not possible given our laws of nature, but there are logically possible worlds where the laws of nature are different, and permit pigs to fly). If you can fully and accurately imagine a state of affairs, and there is no contradiction in this state of affairs, then the state of affairs is logically possible.
The key issue, then, is whether we can in fact fully and accurately imagine ourselves (our minds) existing in the absence of our bodies. I can imagine myself continuing to think and experience after the destruction of my body and brain: I can look down at the building where my body was burned, move about as I like in my newly disembodied condition. I can imagine exactly what this would be like. So does this prove that it is logically possible for my mental life (and so my mind) to continue on in the absence of my body/brain?
It depends. Let us agree that I can imagine exactly what it would be like to exist independently of my body – it’s just like this except that I have no bodily experience of any sort – I continue to see, think, hear, etc. There are two claims to consider:
The transparency thesis: The complete nature of conscious states are revealed to the conscious subject who has them; nothing is concealed.
The opacity thesis: Although we know a good deal about conscious states just by having them (I know what pain feels like when I am experiencing pain), there are certain aspects of conscious states that are hidden to introspection – there is more to our experience than is revealed in our experience.
If the transparency thesis is true, then there is nothing about my conscious life that is concealed from me; when I imagine my conscious mental life continuing on in a disembodied condition I know everything there is to know about what this mental life involves, and since it doesn’t appear contradictory in any way it isn’t contradictory in any way – since there’s no distinction between appearance and reality for consciousness – so what I am imagining is logically possible.
But suppose the opacity thesis is true: there may be more to my conscious mental life than I can discern through introspection, there is a distinction between appearance and reality for consciousness. If so, although I can clearly imagine existing in a disembodied condition, what I am imagining may not be logically possible. Why? Because it could be that my ordinary conscious states are – in fact – identical with neural states, even though this isn’t discernible through introspection. When I imagine existing in a disembodied condition, I imagine my stream of consciousness continuing on just as it actually is in the absence of my body/brain – but if my consciousness actually consists of neural activity (though this is concealed from me), then the state of affairs I am imagining could not possibly occur: for consciousness like this to exist requires neural activity. Or to put it a different way, when I am imagining experience existing independently of matter, what I am in fact imagining is neural activity, and so the claim that experience could exist in the absence of matter is inherently contradictory.
I haven’t stated this argument very carefully, but perhaps you can see the general idea: if the opacity thesis is true we cannot be sure that all the essential features of experience are known to us; in which case, although we may be able to form a clear idea of what it would be like to exist without a body or brain, this clear idea may not be complete, and so we cannot be certain that what we are imagining is logically possible.
The argument from imaginability hinges on whether the transparency thesis is true. Is it? Nothing is obvious here. But we can draw at least this conclusion: dualism is not obviously false, and so is worth looking at more closely. What are the problems faced by dualists? Are they fatal, as physicalists often maintain?
Against Dualism
I want to look at four arguments used against dualism by its opponents. I go into the third of these “the individuation objection” quite a long way – if you find the depth-metaphysics troubling, move on to the causation problem.
(1) Conception and Connection
A common objection to traditional substance dualism runs thus:
You say that you now – the whole human being - are a combination of two distinct entities, a mind and a body. At what point during the life of your body did your soul become attached to it? At the moment of conception? When you were born? When you reached your first birthday?
Although there’s clearly a difficulty in discovering the time at which attachment occurs (since we can’t observe immaterial minds), it’s not obvious that this is a fatal problem for the dualist, who can reply “Well, OK, we don’t know when souls become attached to bodies, but we know that they do – we wouldn’t exist as beings-with-minds otherwise. All we can say for certain is that it happens sometime before we are three or four – the time most people can remember clearly.”
In fact, this is just one of several awkward problems the dualist faces. When do souls become detached from bodies? When the heart stops, when the brain degenerates beyond a certain point? Do all human beings have immaterial minds – do severely brain-damaged people have them? Is it possible they don’t?
However, the dualist may reply that one day we may be able to answer these questions: if souls causally interact with brains, when we know more about brains we may be able to detect the presence/absence of soul interference. Current neuro-science is just too primitive.
But there is a deeper problem here: not when does attachment occur, but why? Given that immaterial minds are not part of the physical world, why is it they become attached to human bodies in the first place? Why don’t they linger on in their non-physical realm forever?
Again, this isn’t a fatal problem – there are some questions we just don’t know the answer to – and it isn’t a problem at all for those who believe God does the “hooking up”, but this sort of problem is not faced by non-dualists, and to this extent the difficulties dualism faces here count against it.
McGinn’s “hyperdualism”, which posits two interacting realms, one physical, one non-physical, give the dualist a response (albeit lacking in detail) to these objections: it’s natural law (suggests McGinn) that the mental realm “makes contact” with the physical when the physical achieves certain levels of organization, such as are found in young human brains.
(2) Correlations, Dependency and Drunkeness
As I have frequently stressed, although there’s a great deal we still don’t know about how the brain works, we know that a good deal about which mental functions are associated with which brain areas – or at least, we know that damaging certain brain areas produces certain very specific mental deficits.
Does this detailed evidence of mind-brain correlation refute dualism? The answer is no. Correlation is one thing, identity another: the fact that certain mental activities are correlated with certain kinds of brain activities doesn’t mean the mental activity just is the brain activity. It could be, for example, that the brain is a complex receiving/transmitting device (for sending/receiving signals to/from the immaterial mind with which it is in contact), and different sorts of signal are handled by different parts of the brain.
Potentially more dangerous to dualism is the evidence we have that mental activity depends on brain activity of certain sorts. Damage to one specific region of the brain – e.g. Broca’s area – results in highly specific mental deficits – in this case problems using language. There are many specific mental deficits known to be associated with specific brain regions, such that if the relevant region is damaged, the deficit occurs.
There are also non-permanent mental deficits which are puzzling for the traditional dualist. Drink to much and you get drunk. What happens when you get drunk? Well, one major symptom is difficulty in bodily coordination: you stagger, find it hard to walk in straight lines, your speech becomes slurred ….
- this sort of problem is easily explained by the dualist: “The brain is a device which passes messages between mind and body; alcohol affects the functioning of the brain, which can no longer pass messages from mind to body efficiently, so the body doesn’t get accurate transmissions from the mind, which is why the body becomes hard to control when drunk.”
But: the effects of alcohol are more profound. Not only do you find it hard to get your body to do what you want, your mind itself is affected: you find it hard to think clearly, your memory is impaired, your personality is altered (more aggressive, more outgoing, fewer inhibitions). Other “mind altering” drugs have other effects. As do degenerative diseases such as Alzheimer’s.
The important point: why can these drugs, which only affect the brain, produce such profound effects on the mind, if the mind is a non-physical entity? The mental effects produced by drugs goes far beyond what one might expect if dualism is true, and the brain (where these drugs act) merely acts as a messenger service between mind and body!
Does this sort of dependency prove that the mind is the brain? Again, the answer is “no”, but the phenomenon does pose a problem for dualists, who have to refine their position … Instead of saying that the brain is just a transmitting/receiving device, dualists have to say something like this:
The mind is a non-physical thing, which is in causal commerce with the brain; but the brain does more than transmit and receive messages – it actively contributes to the mind’s mental functioning. We know that when we are young (and our brains aren’t fully developed), our mental functioning is different from when we are older – and again, when very old, and our brains degenerate, so too does our mental functioning. We thus know that our brains contribute to our mental abilities – through their interaction with the soul, they enable the soul to have a kind of mental life which would not otherwise be possible. But this sort of dependency is quite compatible with the soul being an entity in its own right.
This moderated dualism may be intelligible, but the concession does weaken the case for dualism: if minds need (in this world) brains in order to function properly, the physicalist’s claim that brains are all you need to have a mental life looks more plausible. But: don’t forget the difficulties of the physicalist!
(3) The Individuation Objection
There’s a familiar slogan "no entity without identity". The idea is that if we’re able to form a coherent conception of an entity X of type F, we have to be able to know the difference between one such entity and two - we have to know on what principle F’s are counted, and if they last through time, this means we have to be able to identify the same item at different times.
Specifying Identity criteria: What does this involve? Answer: stating the conditions for distinguishing one entity from another of the same type at a given time, and the conditions under which earlier and later Fs are one and the same. These are synchronic (at a given time) and diachronic criteria (over time).
Let’s focus on the synchronic criterion - for soul counting. How do we go about counting disembodied souls, or immaterial minds?
Think first of physical objects: suppose we’re concerned with snooker balls - a collection of them at a certain time. How do we count these? What differentiates individual balls? Some balls differ in colour (an intrinsic properties), these pose no problem: it’s easy to say how a blue ball differs from a red one. But how do we distinguish between the red balls? Simple: qualitatively indistinguishable balls can be distinguished by their spatial position. The red balls may all be exactly alike, i.e. qualitatively the same, but they are distinguished by their different spatial locations.
Now think of souls (disembodied immaterial minds), at a given moment t. We could distinguish them by their qualitative features: the thoughts and experiences possessed by each soul at t. This is fine as far as it goes, but what’s to prevent a number of souls having exactly the same kind of thoughts and experiences at t? We can’t rule this out – it’s logically possible - so how would we distinguish souls S1 and S2 that are qualitatively indiscernible?
Crucial point: we can’t appeal to quality, time or space, since souls are non-spatial - we can’t count souls like red billiard balls!
We might say: “OK, the notion of a completely disembodied soul is incoherent, because we can’t specify any criterion of individuation for them. But this objection doesn’t prove dualism false, because actual souls causally interact with bodies, and we can individuate such souls via their bodies.
This is a big climbdown, but also there’s another objection: cf. Strawson:
Suppose I were in debate with a Cartesian philosopher, say Professor X. If I were to suggest that when the man Professor X speaks, there are a thousand souls simultaneously thinking the thoughts his words express, having qualitatively indistinguishable experiences such as he, the man, would currently claim, how would he persuade me that there was only one such soul? (How would each indignant soul, once the doubt has entered, persuade itself of its own uniqueness?)
So even if we grant that the notion of "attachment" or "embodiment" makes sense in the context of dualism (controversial in its own right - the problem of dualistic causation - to come), there’s still a problem: we still don’t have a principle of soul counting - how do we know how many different souls are attached to a given body?
- the subjective evidence won’t suffice: all you know from your own consciousness is that you exist as a single soul
- the third-person perspective only shows you one body - you can’t see how many souls are attached to that body!
Responses? Well, look at the subjective evidence: each thinker thinks, "I exist", and presumably each thinker is right - a basic point of Descartes’ - at least on the assumption (which we won’t question here) that each thought does have a thinker - a mental subject doing the thinking. Doesn’t this suffice? Can’t there be a fact about how many subjects there are, even if there’s no way of counting them up?
Isn’t it the case that subjects, in virtue of being conscious, are self-individuating entities?
The question Strawson asks poses an epistemological puzzle - but our inability to answer it creates no ontological dilemma ... there may be facts that we can’t discover.
Let’s explore this line a little more deeply, beginning first with a look at one of the distinctive features of subjects of consciousness - the unity of their experience ...
Subjects-existence-and the Unity of Consciousness: think for a moment of the general structure of your consciousness. First: what are the components of your consciousness. Second: how are these components organized? The components are myriad:
- thinking going on
- memories, imaginings
- feelings
- perceptual experiences/bodily sensations
You are "aware" of all this going on. We can now ask: what is it that unites these different items? Is it that they are all going on in the same body? They may be - but is does this fact constitute their unity?
No: the different components of your consciousness are all united together within your consciousness. You don’t need to find out that your experiences are connected to a single body to know which experiences are yours!
Two explanations of the unity of consciousness:
(A) A central act of awareness: there’s a point of pure awareness; your visual and auditory experiences, your thoughts, feelings, bodily sensations, these are all united in virtue of being "objects" of this single awareness, falling within it’s "field of view" - so to speak.
(B) Co-consciousness: think of your auditory and visual experiences ... they are quite different, yet "co-present" or co-conscious - they are immediately joined - there’s no "gap" - they appear "together" .... your thoughts are likewise co-conscious with your bodily feelings, and both these are co-conscious with your perceptual experiences. Co-consciousness is a distinctive sui generis relationship between modes of consciousness of different types - nothing mysterious about it - we just can’t explain it in other terms - it’s a primitive feature of experience.
If we accept the co-consciousness view, we don’t need to postulate any additional "act of awareness" - there’s just experiences that occur as parts of unified wholes.
Moral: it doesn’t matter which view we adopt, for present purposes. On either story, the crucial fact is that a subject’s diverse experiences are unified from within experience - we don’t need to appeal to anything external to a subject’s consciousness to make sense of the fact that their experiences are unified.
An Objection and a Crucial Reply: but how do we know that experiences within unified centre of consciousness all belong to one and the same subject? How do we know that different simultaneous centres of consciousness belong to different subjects? Don’t we need the body again?
REPLY: no, for we define consubjective experiences (experiences belonging to one and the same subject) as co-conscious experiences (those featuring within a unified centre of consciousness)
- the unity of consciousness is the basic element: unfied experiences necessarily belong to just ONE subject; different centres of consciousness necessarily belong to DIFFERENT SUBJECTS
The import: the unity of consciousness that is constitutive of subject-hood is not dependent on conscious recognition of one’s own existence - we don’t need to be thinking "I think therefore I am" for our consciousness to exist as unified.
Returning to the main theme: our problem is whether or not it’s OK to disregard the demand that we have a counting principle for subject’s. We now have a better idea of what a conscious subject is - of how their unity is created from within consciousness - so we’re half-way there
- for, if we had used the notion of a SUBJECT qua immaterial substance to explain what makes different experiences consubjective, before having an acceptable account of the concept of a substantial SUBJECT, we’d clearly be guilty of begging the question
- but we have found a way of allocating experiences at-a-time to different subjects which doesn’t make any use of the notion of a subject - the only appeal was to relationships between experiences
But the main problem remains: the objection runs: consider two qualitatively indistinguishable souls or subjects, two spheres of consciousness that are each having exactly the same type of experience at a given moment (or over their entire careers) - what makes them two rather than one? In the case of the red billiard balls, we have an answer: the balls have different spatial positions, but souls don’t have spatial positions, so we lack an account of their individuality ...
One reply: the spatial account of individuality is fine for physical objects, because they are spatial, they exist in a common space - but since souls don’t, why think the same principle should be applicable - it’s obviously irrelevant in the mental context ...
This maybe right, but it can be reinforced.
Matter, Space and Individuation A simple line of argument suggests that even within the physical scheme of things, some items are ontologically basic - in the sense that no account is provided of their individuality
In the case of the red billiard balls, we account for the numerical difference between the balls in terms of spatial location ... this presupposes that space is independent of physical objects - the existence of space is being taken for granted.
This maybe OK, but we must beware of adopting too simple-minded a view of the relationship between objects and space. There are two general views about this relationship:
Spatial substantivalism: take space to be an object in its own right, whose existence and identity are independent of its occupants
Spatial relationalism: space doesn’t exist as an independent substance; space exists only as a set of relationships between physical objects
Now, we don’t need to decide between these options to undermine the objection against souls:
(A) If we adopt the relationalist position, then it’s clear that physical objects are being taken as primitives: the identity and individuality of each basic physical object is NOT dependent upon it’s spatial position, it’s not dependent upon ANYTHING ELSE AT ALL -
- the existence of space depends upon the existence of objects - space comes into being as a result of the relationships between objects -
- so if we ask the question: what accounts for the fact that two red billiard balls are different objects, we can’t answer: they exist at different places - since the existence of places is dependent upon the objects
(B) If we adopt the substantivalist position, then space is a primitive object in its own right. We can now account for the distinctness of the billiard balls by pointing to their different spatial locations. But a new problem confronts us: what accounts for the individuality of space itself?
This might seem an odd question. Surely there can be only one space .... Kant said so, so it must be true. Wrong.
The reason for thinking there can be only one space is that space is common-sensically taken to be infinite in extent - if our space stretches on forever in every direction, there’s no room for any more space....
But see how we’ve already begged the question: what do you mean there’s no room? No, there’s no room in our space, since the hypothesis in question is that there might be more than one space .... if there were more than one space, then the other spaces wouldn’t be located in our space - they are each their own spaces.....
- and if the different spaces were located in some OTHER space, they wouldn’t be different spaces at all, just different regions of a single space
So the objection that there can’t be any room for other spaces is empty ...
The flatland analogy: many two-spaces stacked in three-space, many three-spaces stacked in four-space ...
- this is one way for there to be room for plenty of spaces of OUR kind, but each 3-space is really only a region of a bigger space - we want different spaces altogether
In fact, many philosophers have argued for the logical possibility of a multiplicity of different physical spaces ... Quinton’s Lake-land thought-experiment ...
The moral again: if there’s no reason to rule out the logical possibility of many spaces, we have no answer to the question: what makes these spaces distinct? Each space is a primitive object, from the point of view of individuation ...
So, either way, some sort of physical item is taken as primitive from the point of view of individuation .... if it’s OK to take an item to be primitive in this way, why not take MINDS or souls to be primitive from the point of view of individuation?
NOTE: to say that minds are too strange and insubstantial is begging the question against the dualist, who maintains that the universe contains two fundamentally different kinds of entity, physical and mental. The mental is only strange and thin from the perspective of the physical - the physical is strangely inert and lacking in quality from the perspective of the mental.
(4) The Problem of Dualistic Causation
What exactly is the causal problem? The general direction is clear enough: many have argued against the view that an immaterial entity could causally interact with a physical entity such as a brain. But there are in fact a number of different arguments which lead to this conclusion.
(A) The Intelligibility of Dualist Causation
The claim: it makes no sense to suppose that an immaterial entity could causally interact with a material entity.
Before proceeding it is important to note that this claim – even if true – doesn’t refute all forms of dualism – only the interactionist form is under threat. The parallelist and epiphenomenalist don’t claim that interaction takes place!
But since interactionist dualism is the most appealing form of the theory, most dualists will want to counter the “unintelligibility” charge.
The objector says “We can’t make sense of immaterial things causally interacting with material things”. What’s the problem supposed to be? A common claim is this:
If minds are immaterial substances, they don’t occupy physical space. How can something spatial causally interact with something non-spatial?
This general worry can be developed in several ways:
(1)Physical causation = causation by contact
Familiar forms of physical causation works on the model of billiard balls: one thing changes or influences another by touching it somehow - contact in space. This is how we see: photons reflected off physical objects hit our eyes ... this is how many chemical interactions occur: atoms interacts with atom by contact. If this causation necessarily requires spatial contact, then psycho-physical causation is clearly logically impossible.
BUT: there’s no a priori reason to think all physical causation IS by contact. Gravity and magnetism were once thought to work by action-at-a-distance: something here makes a causal difference across vast reaches of space - the Earth gravitationally attracts every other object in the entire universe.
- this isn’t how gravity is now thought to work, but it used to be - and the reason why gravitational theory changed wasn’t solely because of conceptual objections to the idea of action at a distance.
So, if causation needn’t work by spatial contact, we’ve yet to see why dualistic psycho-physical causation can be ruled out a priori!
(2) The unintelligibility of dualistic causation
It’s sometimes held that the very idea of causal relations between immaterial events and physical events is simply unintelligible - it’s impossible because it doesn’t make sense.
The objection clearly presupposes that we can make sense of causation in the physical realm. This is partly based on the idea that physical causal relations work by contact - if the bullet kills you by stopping your heart, we can understand the causal mechanism here - the bullet causes massive damage when it hits your heart at very high speeds.
BUT we’ve already seen that not all physical causation works by contact.
ALSO: do we really understand why physical objects have the causal powers they do? Basic physical objects are governed by certain laws ... so it’s a law that electrons repel each other, and settle into various orbits around atomic nuclei ... but why do these laws obtain? Why do bodies attract one another by gravity? We have no idea: it’s a brute fact that certain objects fall under certain causal laws .... the bedrock of physical causality is not intelligible at all really.
- so dualistic causation is no worse off.
BUT: it remains true that psycho-physical causation is a funny business ... it seems as if our experience and behaviour depend on billions of neurones interacting - it’s not easy to see how an immaterial mind could be hooked up to such a system - but this isn’t to say it’s not possible!
/I<(3)> Foster’s Causal Pairings Objection
Suppose there were causal relations between immaterial minds and bodies. There must be psycho-physical laws: these will connect the properties of minds and bodies. A mind in a certain condition will affect a body in a certain way, and vice-versa.
- in other words, there’ll be certain law-like regularities between types of physical event and types of mental event.
The nomological assumption: when an event E1 causes E2, the causal relation exists in virtue of the intrinsic properties of E1 and E2 and certain covering laws, e.g. there’s a law that says heating a piece of lead causes it to melt. E1 is a heating-of-lead event, and E2 is a melting-of-lead event.
Problem: suppose we have two exactly similar bodies, B1 and B2, each attached to a mind, M1 and M2, which are also exactly similar, and simultaneous. Pushing a pin into each body at the same moment will produce the same kind of mental event: a certain sort of pain, P1 and P2, in M1 and M2. The question: how can we make sense of the idea that pushing a pin in B1 produces a pain in M1 rather than M2? How can we make sense of the idea that B1 is causally hooked up to M1 but not M2?
The problem is that causal laws relate types: suppose it’s a law that an Phi-type physical event (pin insertion) produces an psi-type mental event (sharp pain) half a second later. This kind of law wouldn’t enable us to say that pushing the pin in B1 causes the pain in M1 rather than M2 ...
- this kind of law doesn’t allow us to make sense of the claim that B1 is causally related to M1 alone, which we need to make sense of if we’re to make sense of psycho-physical interaction
It would be OK if we could say that B1 and M1 were spatially contiguous, or closer than B1 and M2 - but this isn’t an option here!
The obvious answer: psycho-physical laws relate bodily and mental events - in the case of B1 and M1, sticking a pin in B1 produces a pain in M1 rather than M2 because M1 is embodied in B1, but not B2.
BUT: the notion of "embodiment" here relies upon psycho-physical causation!
The better solution: appeal to scope-restricted laws, laws which make explicit mention of particular entities. So take Smith’s body and mind, B-s & M-s and Brown’s body and mind, B-b and M-b: there are two laws:
- a phi-type event in B-s causes a psi-type event in M-s half a second later
- a phi-type event in B-b causes a psi-type event in M-b half a second later
These laws are restricted to particular entities - but is there any reason to think such laws are impossible? Note, it’s the case for each human subject that their minds and brains are related by scope-restricted laws, so there’s nothing special about Smith and Brown.
Rejecting the assumption: Foster’s heated sphere example: suppose we have a sphere of type N, that when struck causes a flash to appear anywhere within a foot of it; now suppose we have two spheres, N1 and N2, which we place close together (six inches). We strike both at the same time, and two flashes occur, close together - each flash could have been produced by either sphere ... so the laws governing the flash productions don’t suffice to uniquely pair cause with effect - yet we can make sense of the idea that each flash is causally produced by a different hitting event.
(B) The Causal Closure of the Physical Realm
The “causal closure” principle amounts (roughly) to this: the only causal influences on physical events are other physical events, so physical systems are “causally closed” to non-physical influences. If true, this principle only poses a problem for interactionist dualism – it doesn’t effect epiphenomenalists (and parallelists), who are dualists who deny that minds causally influence brains. So the causal closure principle doesn’t in itself rule out dualism, at most it rules out one form of dualism – it just happens that this form is the most appealing form – it’s hard to believe that nothing that happens in our minds causally influences what our bodies do!
Interestingly, in recent years many physicalists have used the closure principle to argue for physicalism. Here’s how Foster formulates the argument (The Immaterial Mind, 186-7):
1.On the basis of physical science we should accept:
(a) To the extent that they can be causally explained at all, the physical conditions obtaining at any time can, from a God’s-eye view, be fully causally explained purely in terms of the preceding physical conditions and the framework of physical laws.
2.From (a), we can legitimately conclude:
(b) The physical world is a “closed system”, in the sense that the only causal influences on what occurs within it (at least at any time later than its initial time, if it has one) are themselves physical.
3.But irrespective of physical science, it is clear that:
(c) Mental events often have a causal influence on the subsequent course of the physical world.
4.The only way of reconciling (c) with (b) – the only way of reconciling the causal efficacy of the mental with the fact that the physical world is a closed system – is by concluding:
(d) Mental events are themselves physical.
This argument takes it for granted that epiphenomenalism is false; it assumes (c) that mental events are causally influential on the physical world, and uses the closure principle to argue for the conclusion that mental events must themselves be physical: it is only by being physical that they could causally effect bodily movements. The argument seems valid: if the first three premises are true, so is (4). The only question is whether it is sound: are all the premises true?
One response open to the dualism is to embrace epiphenomenalism, but since this is a desperate move, and few dualists will want to make it. What other response is available? There are at least two.
(i) Embracing Overdetermination
Note the move from (a) to (b). Is it compelling? Well, it may be plausible, but there is a way of accepting (a) but rejecting (b). According to (a) every physical event that occurs can be causally explained (if it can be explained at all) by an earlier physical event. According to (b) the only causal influences on physical events are other physical events. This is a different and stronger claim. Indeed, there is a way for (a) to be true but (b) to be false.
Jim is doubly unfortunate: he’s about to die, not from one cause but from two. A bullet is speeding towards his head, and a poison in his bloodstream is about to create fatal brain damage: the bullet and poison will “hit” at precisely the same time. Jim’s death is “causally overdetermined”, i.e. there were two earlier events each of which was causally sufficient for it. The poison would have killed him by itself, likewise the bullet.
Causal overdetermination seems possible. So the dualist can say:
It is true that all physical events have prior physical causes; but some physical events in the brain also have prior mental causes which are themselves sufficient for their physical effect. The neural events in the brain that are caused by events in the immaterial mind are overdetermined. They have both mental and physical causes.
This is a neat reply, but also troubling … our bodies would continue to “act” in just the same way even if they weren’t connected to immaterial minds – the presence of minds doesn’t make a real difference to the world … Is this easy to believe?
(ii) Rejecting Closure
Premise (a), the claim that all physical events which have causal explanations have purely physical causal explanations, is widely accepted, but is it true? Might it not be that some physical events – those in human and animal brains – have only mental causes?
Why believe (a)? Is it because we have detailed knowledge of how our brains work, and have discovered that no physical occurrences in our brains lack physical causes? No. At present we cannot investigate brains in this sort of detailed way: they are far too complex. Our knowledge is sketchy and partial.
The evidence for (a) is indirect. Investigations of physical systems in general (without specific reference to brains) suggest that the workings of physical systems are entirely explicable in physical terms, e.g. by the mechanisms familiar from chemistry and physics.
Now, as Foster points out (op.cit. 199-200):
… if this is the nature of the scientific case for supposing that the workings of the brain can be causally explained in purely physical terms, then it is a conspicuously weak one. For since the crucial evidence is of this indirect kind – evidence drawn, not from brain research, but from the more basic investigations of physics and chemistry into the nature and behaviour of things in general – it has to be evaluated in the light of whatever else we independently know, or have reason to believe, about the special relationship between the human body and the human mind, and about the role which the brain plays in this relationship. Of course, if all we knew about the brain was that it was a physical object of a certain physical type, it would be reasonable, prior to direct investigation, to suppose that its functioning would turn out to be explicable in terms of the same laws of physics and chemistry as other physical things – that anything distinctive in its internal behaviour would be attributable to its distinctive physical properties rather than to some sui generis source of causal influence. But, in fact, we already know that the brain is the seat of the mind; and al that we pre-scientifically know about ourselves suggests that the mind, qua mind, has a causal influence on behaviour. When the scientific evidence is evaluated in the light of this information, and when we also take into account our refutation of the type-identity thesis [and other physicalist accounts of mind], the rational conclusion to draw is that the brain is subject to certain non-physical influences which do not affect the other physical systems which science investigates; and in default of any special reason for postulating overdetermination, this in turn would make it rational to believe that the workings of the brain are not fully explicable in purely physical terms. The point is not that the scientific evidence gets overruled by other considerations … It is rather that the significance of this evidence can only be properly assessed in a wider context, and that in this context, it simply does not support the conclusion that the brain functions in a way which could be wholly accounted for (even from a God’s-eye view) on the basis of its physical character and physical laws.
Quite a plausible point!
Conclusion: causation isn’t the insuperable problem for the dualist that its often taken to be. Nonetheless, dualism faces other difficulties (remember the drunk), even if none are straightforwardly fatal. But so too does physicalism/materialism ….
(1) I should point out that the term “substance” is used in different ways by different philosophers. Some use it just to mean object (as opposed to “property”); others use it to refer only to objects of a special sort, e.g. objects which do not depend on any other objects for their existence. I won’t be going into this vexed issue here. Note that Descartes used “substance” in the second way, and so was led to the view that there was only one “true substance”, namely God, who doesn’t depend on anything else for His existence.