Damascene Philosophy

QuestionsVI

Is the mind just the brain?

Thoughts seem to have no weight, colour or location. Brains have all three. How are the two related?

Reading time
5 min
Difficulty
Introductory
Branch
Mind
First posed
Plato, Phaedo, c. 380 BCE; set in modern form by René Descartes, 1641

The question

Your brain weighs about one and a half kilograms. It sits in your skull, has a temperature, and can be photographed. Your thought about your grandmother's kitchen has none of these features. It has no mass, no shape and no location you could point a scanner at. It is about something, a kitchen far away and long ago, which seems to be a property no lump of matter could have.

And yet the two are obviously connected. Drink alcohol and your thoughts change. Damage a part of the brain and a person can lose the ability to recognise faces or form new memories. Decide to raise your arm and, somehow, it rises.

The mind-body problem asks what the relationship is. Is the mind a separate thing that interacts with the body? Is it simply the brain under a different description? Is it what the brain does, the way digestion is what the stomach does? Or is the physical world itself, in some sense, mental?

“I think, therefore I am.”

René Descartes, Discourse on the Method (1637)

Why it matters

Your answer decides what you think you are. If you are a non-physical mind, you might survive the death of your body. If you are your brain, then you are a particular piece of biology, and when it stops, you stop.

It also shapes medicine and technology. Whether depression is best understood as a brain disorder, a disorder of thought, or both; whether a machine could ever have a mind; whether a person could be uploaded to a computer: each depends on how mind and matter are related.

Key terms

  • Mind-body problemThe problem of how the mind, with its thoughts and feelings, is related to the body and brain.
  • Substance dualismThe view that the mind is a non-physical thing, a separate substance from the body, though the two interact.
  • PhysicalismThe view that everything that exists is physical, or is fixed by the physical facts.
  • FunctionalismThe view that mental states are defined by what they do, their causal roles linking inputs, other mental states and behaviour, rather than by what they are made of.
  • IntentionalityThe 'aboutness' of mental states: the way beliefs, desires and perceptions are directed at or represent something beyond themselves.
  • Causal closure of the physicalThe principle that every physical event that has a cause has a sufficient physical cause. If true, it leaves no obvious room for a non-physical mind to make a difference.

The positions

Position I

Substance dualism

The mind is a non-physical thing, distinct from the body, which interacts with it.

Position II

Identity theory

Mental states are brain states. A pain just is a certain pattern of neural activity, as lightning just is electrical discharge.

Position III

Functionalism

A mental state is defined by what it does: its causes, its effects, and its relations to other states. Any system that plays the right roles has a mind.

Position IV

Idealism

Reality is fundamentally mental. Matter is either a construction of minds or appearances within them.

Arguments and objections

Substance dualism

Best argument
René Descartes argued that he could clearly conceive of his mind existing without his body, since he could doubt that he had a body but not that he was thinking. Whatever can be clearly conceived apart can exist apart, so mind and body are distinct. The view also fits how experience seems from the inside: the self does not feel like a lump of tissue.
Strongest objection
Princess Elisabeth of Bohemia put the decisive question to Descartes in 1643: how can an unextended, immaterial soul push a material body? Modern physics sharpens it, since energy appears to be conserved and every physical event seems to have a physical cause, leaving no gap for a soul to act through.
The reply
Some dualists respond that the conservation laws apply only to closed systems, or that the mind might act by influencing quantum events without adding energy. Others accept that the interaction is a brute fact, no stranger than gravity acting at a distance once seemed.

Identity theory

Best argument
Science routinely discovers that two descriptions pick out one thing: water is H2O, heat is molecular motion. The close correlation between mental and brain events is best explained by identity, which is simpler than positing two kinds of thing in lockstep.
Strongest objection
If pain is one specific human brain state, then an octopus or an alien with a different nervous system could not feel pain, which seems wrong. Hilary Putnam called this the problem of multiple realisability.

Functionalism

Best argument
Pain is whatever is caused by damage, produces distress and avoidance, and makes you want it to stop. Neurons in humans, different tissue in octopuses, perhaps silicon in robots could all play that role. This explains multiple realisability and fits cognitive science, which models the mind as information processing.
Strongest objection
It seems to leave out experience. A system could play every functional role of pain without anything feeling painful. Searle's Chinese Room argues similarly that running the right program is not enough for understanding.
The reply
Functionalists answer that the intuition of something left over may itself be a product of how we represent our own minds, and that the Chinese Room confuses a part of the system with the whole.

Idealism

Best argument
We never encounter matter except through experience. George Berkeley argued that the idea of something existing wholly unperceived is incoherent. Modern versions suggest that what physics describes is the structure of a reality whose intrinsic nature is experiential.
Strongest objection
Idealism struggles to explain why the world behaves so regularly when no one is looking, and why it existed for billions of years before any minds evolved.
The reply
Berkeley's answer was that God perceives everything continuously. Contemporary idealists appeal instead to a universal consciousness or to the regularities of experience itself.

Who argued what

Where you stand

What is the mind?

Choose one to see how people answer.

Variations

The brain in the scanner

Suppose a future scanner can display your thoughts on a screen with perfect accuracy. Does that show the thoughts are physical, or only that they are perfectly correlated with something physical? The same evidence fits both views, which is part of why the problem is so stubborn.

Leibniz's mill

Imagine a thinking machine enlarged until you can walk inside it like a mill. Inspecting it, you would find only parts pushing on one another, never a perception. Gottfried Wilhelm Leibniz took this to show that perception cannot be mechanical. Physicalists reply that you also would not see digestion by looking at a single cell.

Go deeper

Why 'causal closure' matters so much

The principle of causal closure of the physical says that every physical event that has a cause has a sufficient physical cause. If it holds, then a non-physical mind has nothing left to do: your arm would rise because of neurons whether or not a soul chose to raise it. Much of the modern case for physicalism rests on this principle, and much of the dualist response consists in questioning it.

Intentionality: the other mystery

Besides experience, minds have intentionality: thoughts are about things. A thought can even be about something that does not exist, like a unicorn. Franz Brentano argued in 1874 that this 'aboutness' is the mark of the mental. Explaining how physical states can be about anything is a separate, and equally difficult, problem.

Related ideas

Question

Why is there something it is like to be you?

Science can explain what the brain does. The hard problem asks why any of that doing is accompanied by experience at all.

Thought experiment

Could there be a zombie you?

Imagine a being physically identical to you, atom for atom, who acts exactly as you do but feels nothing. If that is even possible, consciousness is something extra.

Thought experiment

The Chinese room

A man in a room follows a rulebook to answer questions in Chinese perfectly, without understanding a word. Is that all a computer ever does?

Question

Could a machine be conscious?

Machines can now talk, reason and seem to care. Whether anyone is home inside them is a different question, and no one knows how to answer it.

Thought experiment

Two minds in one head?

When surgeons cut the connection between the brain's hemispheres, each side began to act as if it had a mind of its own.

Thought experiment

Could you upload your mind?

If every connection in your brain were scanned and run on a computer, would the program be you, a copy of you, or no one at all?

Further reading and sources

Open questions

  • If your mind is your brain, what exactly would it mean for you to survive death?
  • Could two beings be physically identical but mentally different?
  • Is 'physical' a clear enough idea to settle this question?

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