Substance Dualism Flashcards
The indivisibility argument for substance dualism (Descartes).
In Meditation II, Descartes argues that mind and body have different essential properties – thought and extension. He understands thought in terms of consciousness and Intentionality; extension is the property having a size and taking up space. In Meditation VI, Descartes claims that this provides an argument that mind and body cannot be the same thing: if they were the same thing, they would have the same properties.
THE MENTAL IS DIVISIBLE IN SOME SENSE
Descartes’ claim that we will, think, imagine, with the whole of our minds, not a literal part, is appealing. However, cases of mental illness, e.g. multiple personality syndrome, might be used to suggest that the mind can be divided. In such cases, it seems that some ‘parts’ of the person’s mind are unable to communicate with other ‘parts’. Theories of the unconscious suggest something similar: people may believe or desire one thing consciously and the opposite thing unconsciously. So it makes sense to talk about ‘parts’ of the mind.
However, Descartes could respond that the way in which the mind is ‘divisible’ is entirely different from the way in which the body is. Bodies are spatially divisible, while minds are only functionally divisible. The different ‘parts’ do different things, but they aren’t in different spatial locations. So his argument that mind and body are different because they have different properties is unchallenged.
NOT EVERYTHING THOUGHT OF AS PHYSICAL IS DIVISIBLE
Is it true that physical substances are always divisible? When Descartes argued that extension is the essential property of physical objects, and that what is extended is divisible, was he right? We may question whether this theory of physical objects is correct. It was a matter of some debate in the seventeenth and eighteenth centuries whether physical objects are infinitely divisible. If you cut something up, can you always cut it into smaller pieces? The question is not whether we can actually do this right now, with the technology we have, but whether there are physical things that cannot be divided even in principle. If, for example, the smallest physical particles are best understood as packets of energy or force fields, then we can’t further divide these – you can’t have half a force field! Or again, perhaps not only force fields but also processes or waves or something else that can’t be divided spatially form a fundamental part of the physical universe.
One possible response is that even if force fields or waves can’t be divided in reality, we can still conceive of them having half the size. In that sense, we can still talk of spatial ‘parts’. There is no logical limit to how small spatial parts can be. However, whether this is true or not may depend on the best physical theory of what space is. If we need to change our concept of space, then perhaps there will be such a limit.
The implication of these reflections is that it may not be an essential or defining property of every physical substance that it is divisible. There are some indivisible things, such as force fields, that are physical. In that case, the fact that the mind is not divisible does not entail that it is not physical. It could be a form of non-divisible physical thing. So even if Descartes is right that the mind isn’t divisible, this doesn’t prove that it isn’t physical.
This line of thought does not show how the mind could be a non-divisible physical thing. After all, the mind is very different from subatomic particles! The objection only seeks to show that Descartes’ divisibility argument, as it is stated, fails.
DESCARTES CONCEIVABLE ARGUMENT
P1- I have a clear and distinct idea of myself as something that thinks and isn’t extended
P2 I have a clear anand distinct idea of bosh as something that is extended and does not thing
P3- if I have a God and distinct thought of soemthing, God can create it in a way that corresponds in my thought
C1 Therefore,God can create mind as something that thinks and isn’t extended and body as something that is extended and does not think.
C2- therefore mind and body can exist independently of one another
C3- therefore, mind and body are two distinct substances
MIND WITHOUT BODY IS CONCIEVABLE
Many philosophers believe that Descartes’ conceivability argument doesn’t work. Objections to an argument either challenge the truth of one of the premises or they challenge an inference. On the simplified version of the argument, there is only one initial premise, (P1) ‘It is conceivable that mind can exist without body’. There are then two inferences. First, Descartes infers possibility from conceivability – (C1) because it is conceivable that mind can exist without body, it is possible that mind can exist without body. The second inference is (C2) from the possibility that mind can exist without body to substance dualism. We will look at an objection to each stage of the argument. We start by challenging (P1).
Is Descartes right about that we can conceive of mind and body as separate substances, that we can conceive of mind existing without body? Or more precisely, is he right to claim that we can do so clearly and distinctly? Descartes assumes that he can identify what it is to think from introspection. But what is thinking, really? What is its nature? If we knew the answers to these questions, we may find that we cannot clearly and distinctly conceive of thought (mind) without the body. Descartes may think that it is conceivable that mind and body are distinct substances when, in fact, it isn’t conceivable. He may be confused or simply lack relevant information.
For example, the theory philosophical behaviourism argues that the mind – mental states and events – should be analysed in terms of behaviour. To talk of beliefs, thoughts, desires, choices and so on is to talk of how something behaves. Now, without a body, something can’t exhibit behaviour; and without behaviour, there is no mind. If this theory is correct, then once we’ve understood what we mean when we talk about the mind, we will realise that mind without body is inconceivable.
This is a very strong claim. For example, if it is right, then disembodied minds, such as God, are inconceivable. And yet for most of the history of humanity, people have claimed to be able to make sense of the idea of God. So, we may object, defending Descartes, that it is likely that philosophical behaviourism is wrong to think that in talking about mental states, we are talking about behaviour. And so mind without body is conceivable.
However, philosophical behaviourism provides just one argument supporting the claim that mind without body is inconceivable. There may be others. The general point is that we can make mistakes over what we think is conceivable.
Descartes accepts this. We can make mistakes, which is why we must get our ideas clear and distinct first. His claim is that we can’t make mistakes with clear and distinct ideas. So to object to the first premise of the conceivability argument, what we actually need to argue is one of two things. Either we cannot clearly and distinctly conceive of the mind as separate from the body – as the analysis of philosophical behaviourism claims. Or we can challenge Descartes’ theory of clear and distinct ideas guaranteeing truth. Perhaps we can make mistakes concerning even what we conceive clearly and distinctly.
WHAT IS CONCEIVABLE MAY NOT BE METAPHYSICALLY POSSIBLE
Let us suppose that we can conceive of our minds and bodies as distinct substances. Just because we can, this doesn’t mean that our minds and bodies really could be distinct substances. Perhaps to exist at all, minds must depend on bodies in some way that we don’t know about. This objection challenges the first inference in Descartes’ (simplified) argument.
To understand the objection, we first need to clarify what is it for something to be ‘metaphysically possible’. And to do that, we first need to understand physical possibility and logical possibility.
WHAT IS CONCEIVABLE MAY NOT BE METAPHYSICALLY POSSIBLE
Physical possibility - Call the world we live in, as it is in fact, the ‘actual world’. This world has particular laws of nature, such as the law of gravity and e = mc2, and physical constants, such as the speed of light. These laws and their application to physical objects define what is physically possible. For instance, it is not (physically) possible for human beings to fly unaided (on Earth), because the upward thrust they can generate using their bodies cannot exceed the force of gravity. What is physically possible is what is possible given the laws of nature as they are in the actual world.
WHAT IS CONCEIVABLE MAY NOT BE METAPHYSICALLY POSSIBLE- LOGICAL POSSIBILITY
Logical possibility is easiest to understand by relating it to analytic and synthetic propositions. All meaningful synthetic propositions describe what is logically possible. True analytic propositions describe what is logically necessary (what must be the case). False analytic propositions describe what is logically impossible (what cannot be the case). For example, it is logically impossible for there to be a square with three sides. The phrase ‘a square with three sides’ is conceptually incoherent, i.e. the meanings of the terms contradict each other, and so no such thing can exist. Anything that is not logically impossible is logically possible (or logically necessary).
Logical possibility
o, we can think of logical possibility as conceptual possibility – what our concepts allow as making sense. We can argue that this is the same as what is conceivable – what we can imagine without self-contradiction.
The laws of nature seem contingent, i.e. it seems possible that they could have been otherwise. Light could have gone faster or slower; the ratio of mass to energy could have been e = mc, and so on. Of course, these things aren’t physically possible. But they are, it seems, logically possible. Nothing in the concept of light entails that it must travel at 299,792 kilometres per second. Or again, it isn’t logically impossible that human beings can fly unaided, just physically impossible.
Everything that is physically possible is logically possible (unless our concepts are terribly muddled!), but not everything that is logically possible is physically possible.
WHAT IS CONCEIVABLE IS NOT METAPHORICALLY POSSIBLY
Some philosophers want to stop there, with two types of possibility – physical and logical. But debates in metaphysics, including the metaphysics of mind, over the last 40 years have led many philosophers to argue that there is a third type of possibility, metaphysical possibility. The reason is that analytic truths and necessary truths may come apart.
For example, ‘WATER’ and ‘H2O’ are different concepts, and before the discovery of hydrogen and oxygen, people knew about water. They had the concept of WATER, but not the concepts of HYDROGEN and OXYGEN, and so not the concept of H2O. And so they didn’t know that water is H2O. Even after hydrogen and oxygen were discovered, someone may have thought ‘I wonder whether water is made of hydrogen and oxygen or something else’. So ‘water is H2O’ is not analytically true. On this understanding, it is conceivable, or logically possible, that water is not H2O.
But water and H2O are one and the same thing – the two concepts refer to just one thing in the world. Water is identical to H2O. Now, nothing can be what it is not. So if the property of being water and the property of being H2O are one and the same property, you can’t have ‘one’ without ‘the other’. If A is the same thing B, then A and B can’t be separated – there is just one thing here. So while we have two concepts – WATER and H2O – there is only one property that they both pick out in the world.
What this is means is that, although it is logically possible for water not to be H2O, it is metaphysically impossible for water to be anything other than H2O. It seems that not everything that is logically possible is metaphysically possible.
Why don’t we just say that it is physically impossible for water to be anything other than H2O? This claim is certainly true, but it isn’t strong enough. If the laws of nature are contingent, then perhaps they could be different. Light could still be light but travel at a different speed, couldn’t it? The claim with water and H2O is stronger. Water wouldn’t be water if it wasn’t H2O. If the laws of nature changed, so that hydrogen and oxygen never bonded and there was no such thing as H2O, then there would be no such thing as water. There couldn’t be water, but with a different chemical composition.
We now have a sense of what metaphysical possibility is, and how it is different from both physical possibility and logical possibility. What is metaphysically possible is constrained by the real nature or identity of things. We also have an example of how something could be conceivable but not metaphysically possible, namely thinking that water is not H2O but something distinct. Another example is often used to try to make the point that what we think is distinct may not always be distinct. Suppose I believe that the Masked Man has robbed the bank. I also believe that my father has not robbed the bank. Clearly, I conceive that the Masked Man is not my father. It is logically impossible for one and the same person both to rob the bank and not to rob the bank. Does this entail that it is metaphysically possible that the Masked Man is not my father?
In one sense, we might say that the Masked Man could be anyone – nobody knows who he is. But we also rightly think that whoever the Masked Man is can’t be someone else. No one can be somebody else. I can’t be you, and you can’t be me. So if my father is not the Masked Man, it is metaphysically impossible that my father is the Masked Man. And if my father is the Masked Man, then it is metaphysically impossible that my father is not the Masked Man. (You can run the same argument with Batman and Bruce Wayne…)
Now I can conceive that my father is not the Masked Man (it is logically possible). But this doesn’t show that it is metaphysically possible that my father is not the Masked Man. If the Masked Man is my father, then it is metaphysically impossible for my father to be a different person from the Masked Man. From my conceiving that ‘two’ people are distinct, we cannot infer that it is metaphysically possible that they are distinct.
We can now apply these ideas to Descartes’ argument. Descartes argues that it is possible for the mind to exist independently of the body, because he can conceive of it existing without the body. In other words, he argues that because it is logically (conceptually) possible for the mind to exist without the body, it is also metaphysically possible. But this doesn’t follow. Perhaps unknown to him, the mind is not an ontologically independent substance, and it is metaphysically impossible for it to exist separately from the body (just as it is metaphysically impossible for water to exist without H2O).
WHAT IS CONCEIVABLE IS NOT METAPHYSICAL- REPLY
However, Descartes is happy to grant that we cannot in general infer what is (metaphysically) possible from what we think. But in the case of clear and distinct ideas, the inference is justified. For example, we may rightly claim that it is impossible for a triangle to have internal angles that don’t add up to 180 degrees just because it is inconceivable that they should. Likewise, because he can clearly and distinctly conceive that mind and body are distinct substances, Descartes argues, it follows that it is possible that they are.
This provides a contrast with the Masked Man. My conceptions of my father and the Masked Man are not clear and distinct in the way that Descartes requires. It is only while we do not know who we are thinking of when we think of the Masked Man that we can think that the Masked Man could be anyone. And so, Descartes would argue, the Masked Man fallacy cannot be used as an objection to his argument.
Does this response work against the case of water and H2O as well? Were people who wondered about whether water is H2O simply not thinking clearly and distinctly? Descartes could argue that they were – our sense experience, e.g. of water, doesn’t tell us what water really is. By contrast, he holds, introspection does tell us clearly and distinctly what mind is. We fully understand what the mind is by reflecting on our own mind, and we fully understand what bodies are by reflecting on our experience of bodies. Because we have this understanding, we can know that minds do not dependent on bodies to exist, and are therefore separate substances.
WHAT IS METAPHYSICALLY POSSIBLE TELLS US NOTHING ABOUT THE ACTUAL WORLD.
Suppose that it is metaphysically possible that the mind can exist as a distinct substance. Does it follow that the mind does exist as a distinct substance?
Let us assume, for the purposes of argument, that we conceive of mind as something that thinks and of body as something that is extended. From this, it does not follow that the mind exists as something that thinks and isn’t extended or of body exists as something that is extended and does not think. There is nothing in the initial conceptions of mind and body that oppose each other. There is no contradiction in conceiving of mind as something that is extended and thinks, or again as the thinking part of something that is extended. Likewise, there is no contradiction in conceiving of body as something that is extended, but which may, in some instances, also think. If this is right, then we can conceive of mind and body as distinct substances, or we can think of thought and extension as properties of the same substance.
Assume that whatever we can clearly and distinctly conceive is metaphysically possible. Therefore, if Descartes is right about clear and distinct ideas, it is metaphysically possible that mind and body are distinct substances. But equally, given what was just argued, it is metaphysically possible that thought and extension are two properties of a single substance. What we need to know is which option is true in the actual world. Simply knowing what is metaphysically possible does not tell us which possibility correctly describes reality. So just because it is metaphysically possible for mind and body to be separate substances doesn’t show that they are separate substances.
However, we should accept that what is metaphysically impossible does tell us something about how things actually are in the world, because what is metaphysically impossible cannot exist. If Descartes could show that it is metaphysically impossible for mind and body to be the same substance, that would show that they must be separate substances. So he could argue that we cannot clearly and distinctly conceive of mind and body as anything other than separate substances – just as we cannot clearly and distinctly conceive of a triangle not having internal angles that add up to 180 degrees. Something about our concept of mind, e.g. its indivisibility, means that we cannot conceive of it as extended; and something about our concept of body (what?) means that we cannot conceive of it as having thought. But is this right?
