Mental States and Science

What can science tell us about mental states?

For one, it can tell us that mental states are related to what’s going on in the physical states of the brain. For instance if your brain is denied oxygen, say, from a cardiac arrest, you may go into a vegetative state and lose consciousness (this may have been what happened to to-warmbier-has-extensive-brain-damage-doctors-say-n773036″>Otto Warmbier). Science can also tell us about the relation between specific areas of the brain and mental states. We know, for example, that the area of the brain called the visual cortex is related to seeing. But can science tell us how mental states are related to brain states? Can science explain why the visual cortex, for example, is related to seeing, as opposed to smelling or some other mental state, or no mental state at all?

There is a debate in philosophy of mind about this question. On one side of this debate are philosophers who believe that at present we have no scientific idea of how mental states are related to the physical states of the brain. On the other side of this debate are those philosophers who deny this.  In this post, we will examine one of the central issues underlying this debate, namely whether mental states can be described scientifically.

When we scientifically describe the nature of something in the physical world we think about its properties that can be measured, such as its weight, size, shape and motion, and these properties are understood mathematically. When we scientifically describe something in the physical world we do not think of how it appears to us. Consider, for example, how science describes the nature of water. Science says its two parts hydrogen and one part oxygen (H₂O). Notice that this scientific description does not say how water appears to us – that is, how it tastes or looks or smells or feels or sounds. We could scientifically understand things in the physical world, such as water, as the philosopher Thomas Nagel puts it, “even we had none of our present senses, so long as we were rational and could understand [its] mathematical and formal properties.” [The View from Nowhere – pg. 14]

Can we describe the nature of mental states scientifically? For example, can we describe the visual appearance of red in the way we scientifically describe water – that is, without any reference to how the visual appearance of red appears to us? If the answer is no, then it’s not clear whether we can scientifically understand how mental states are related to the physical states of the brain. But why would anyone believe the answer is no?

If soul dualism is true, then it follows that mental states cannot be described scientifically, since souls are not part of the physical world and mental states belong to souls. But perhaps mental states don’t belong to non-physical souls but rather are physical brain states. Why would would anyone who believes that mental states are physical brain states believe that we cannot describe mental states scientifically? In what follows, I will consider three arguments for this view, the argument from introspection, the zombie argument, and the knowledge argument.

The Introspection Argument

1. You are aware of your mental states when you introspect them.
2. When you are aware of your mental states through introspection you’re not aware of any states that can be described scientifically.
3. So mental states cannot be described scientifically.

There are different ways to understand the view that mental states belong to physical brain states. One interpretation is that mental states are identical to physical brain states. If mental states just are identical with physical brain states, then mental states can be described scientifically, since physical brain states can be described scientifically. But how could mental states be physical? Physical brain states have weight and take up space. If mental states are identical with physical brain states, then a thought or an emotion would have weight and take up space. But when we introspect our mental states we are not aware of them as having weight and taking up space. Therefore, mental states are not physical brain states and cannot be described scientifically.

Those who believe that mental states are physical brain states deny premise 2. They claim that when you introspect your mental states you are aware of physical brain states. You’re just not aware of them as physical brain states. You can be aware of physical brain states in two ways, from the inside and from the outside. When you introspect your mental states you’re aware of your brain states from the inside – that is, from a first-person point of view. When you’re aware of your brain states from the inside they don’t seem to have any physical properties, such as weight or spatial location. If, however, you were to view your brain states from the outside – that is, from a third-person point of view – with an autocerebroscope, a device that allows you to observe your own brain, you would be aware of your mental states as having physical properties. When you view your mental states from the outside they don’t seem to have any of the mental properties, such as feeling a certain way.  To sum up, mental states, therefore, can be understood in two different ways – from the inside through introspection and from the outside through observation. Therefore, it does not follow that mental states are not identical with physical brain states and cannot be described scientifically.

It may be helpful to use an analogy to explain how one thing (your mental states) can be understood in two different ways. Consider a small child who is aware of some water. In being aware of water, the child is aware of some colorless substance. But is the child also aware of molecules containing atoms of hydrogen and oxygen? Yes. The child is aware of H₂O, but the child is not aware of water as H₂O, since he knows nothing about chemistry. So water can be thought of in two different ways, from the way we ordinarily experience it (how it looks and tastes and smells) and from the way the scientist describes it. If water can be described in two different ways, then so can mental states, so the response goes.

The Zombie Argument:

1. If mental states can be described scientifically, then it’s metaphysically impossible for two people to be in the same type of physical brain state but not be in the same type of mental state.
2. You can coherently imagine a world that is molecule for molecule identical to our world. The only difference is that in this imagined world no one has any mental states. The people in this world are physically just like us and act just as we act in our world. Their brain states are physically identical to our brain states. But they don’t think or experience anything or have any sorts of sensations. They are what philosophers refer to as “zombies”.
3. If you can coherently imagine X, then you have reason to believe that X is metaphysically possible.
4. Therefore, you have reason to believe that mental states cannot be described scientifically.

The zombie argument, with it’s use of concepts like “metaphysical possibility” and “coherent imagination,” should remind you of the philosophical argument for dualism. It’s not the same argument as the philosophical argument for dualism since it’s not arguing that mental states could exist without brains. Rather, it’s arguing that mental states cannot be described scientifically.

One response to this argument is that premise 2 is false. It’s not clear whether anyone can coherently imagine a zombie world. This response is similar to a response given to the philosophical argument for dualism.

The Knowledge Argument:

1. It’s logically possible to know the essential feature of anything scientifically describable without ever experiencing that thing.
2. It’s not logically possible to know the essential feature of a mental state without ever experiencing that mental state.
3. Therefore, mental states cannot be described scientifically.

To help clarify this knowledge argument let us consider a version of it given by the philosopher Frank Jackson. In Jackson’s version, there is a super-scientist named Mary who is confined to a black-and-white room her entire life and has never seen any colors, only black and white and shades of grey. She is a brilliant scientist and knows everything scientific to know about colors and color perception. For instance, she knows what type of brain states people are in when they see red things. She knows about the different wavelengths of light associated with different colors. She knows how people use color terminology, that people say that tomatoes and stop signs are red and that grass and cucumbers are green. She knows that red is closer on the color chart to orange than it is to blue. One day she released from her black-and-white room and is shown a red apple. According to Jackson, she comes to know a new fact about color perception, namely what it’s like to see something red. Since Mary knew all the facts about colors and color perception that science can describe, Jackson concludes that there are facts about mental states – in this case, the look of red – that cannot be described scientifically.

We should note that if the knowledge argument is sound, it only applies to mental states that have a certain type of consciousness. When you have  a mental state with this type of consciousness,  such as the look of red or the feeling of an itch, something seems or feels a certain way to you. Sensations and moods and emotions and dreams all can have this type of consciousness. Do all mental states have this type of consciousness? It doesn’t seem so. Cognitive states, such as beliefs, are mental states that don’t seem to have this type of consciousness. I can think about my beliefs and so in some sense I can be conscious of them. But I think this type of consciousness is different than the type of consciousness that an itch has. When, for example, I reflect on my belief that 3 is a prime number my belief doesn’t seem or feel any way to me. In contrast, when I have an itch there is a way it seems or feels to me and the way it seems or feels to me is different than the way an pain or a tickle seems or feels to me.

Some critics of the knowledge argument argue that there is no good reason to believe premise 2. Would Mary know what it’s like to see something red in her black-and-white room before she ever saw anything red? The philosopher Daniel Dennett believes that she would. Many critics of the knowledge argument think that she wouldn’t know what it’s like to see red before ever experiencing something red. These critics accept both premises of the knowledge argument and the assumptions of Jackson’s thought experiment, but they claim that the conclusion that mental states cannot be described scientifically does not follow (see here). Some argue that the type of knowledge that Mary has in knowing scientific facts is different than the type of knowledge she has in knowing what it’s like to see something red. So the knowledge argument commits the fallacy known as fallacy of equivocation. Some argue that the way in which we come to know about things described scientifically is different than the way in which we come to know about our mental states. The evidence Mary uses to know about things described scientifically is different than the evidence she uses to know about what it’s like to see red. In her black-and-white room she learns about colors and color perception through books. She learns about what it’s like to see something red through introspection.