Philoscopia

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Relation to the world· Mind and consciousness

The substrate does not matter

Axis: Can a machine think — Could a machine ever truly think?

To think is to process information in a certain way, whatever the substrate that carries out this processing. If a machine performs the same functions as a brain, there is no ground for denying that it thinks.

Who holds this position

Philosophers 3

Turingexplicit

Turing judges the question "can a machine think?" too dependent on the use of words to be settled, and replaces it with a test, the : an interrogator converses blind with a human and a machine; if they can no longer tell them apart, there is no longer a reason to refuse to one what is granted to the other. To the objection that the machine would still lack consciousness of what it says, he answers that pressing it leads to solipsism: I know others think only by their behaviour, and refusing that same evidence to machines alone is arbitrary. The substrate therefore matters little, a universal machine being able to simulate any discrete-state machine.

"Computing Machinery and Intelligence", Mind (1950)

Chalmersexplicit

Chalmers argues that what carries experience is organizational invariance: it is functional organization that counts, not the matter realizing it. His position here follows from no physicalism: it is because consciousness is for him a fundamental datum, tied to organization by a law of nature, that it tracks that organization whatever the substrate.

"Absent Qualia, Fading Qualia, Dancing Qualia" (1995) · The Conscious Mind (1996)

Dennettexplicit

For Dennett, understanding is not an inner flash added to information processing: it is what a system does whose behaviour shows regularities fine enough that one gains by ascribing mental states to it, what he calls the intentional stance. Against the , he replies that the man with the rulebook is only a cog: it is not he who would understand Chinese, but the whole system, room, rules and ledgers included. To seek in the brain a place where understanding would finally occur would be to reinstate the Cartesian theatre his work is spent dismantling.

The Intentional Stance (1987) · Consciousness Explained (1991)

Arguments and objections
ArgumentThe multiple-realizability argument — The substrate can vary while the mental state stays the same: so it is not the substrate that constitutes it.
  1. We never ascribe a mental state by inspecting a material: we ascribe it to the role it plays in what a being does. It avoids what hurt it, hesitates, learns, corrects itself. That is how we recognize a dog's pain and a child's fear.
  2. Yet the same role is played by very different materials and architectures, which is called : the octopus, whose nervous system is nothing like ours, hesitates and learns; and in humans themselves, after a lesion, a function relocates elsewhere in the brain without the corresponding experience disappearing.
  3. What varies while the mental state stays the same is not what constitutes it: if the substrate can vary while pain remains pain, it is not the substrate that makes the pain.
  4. What remains is what did not vary: the organization, that is, a network of relations between what comes in, what is transformed within, and what goes out. Nothing in that organization mentions carbon, neurons, or the living.

Therefore So demanding a particular material is not a philosophical requirement but a substrate prejudice: whatever realizes the organization thinks, silicon included.

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ObjectionAttacks the reasoningThe China-brain objection — Multiple realizability shows that many substrates will do, not that any will.
  1. The argument holds that any realization of the right organization suffices, whatever the substrate: that is the decisive step, and it comes with no restriction.
  2. Let us push it through: suppose the entire population of a country, equipped with telephones and instructions, reproduces exactly the causal relations of your neurons, one person per neuron. The organization, that network of causal roles, is the same, speed apart.
  3. One would then have to say that a subject appears above that crowd, with its pains and memories, of which no participant has the faintest idea. The conclusion is not merely strange: nothing in the argument says why it would be true.
  4. Either one accepts it, and "thinking" no longer means what we meant; or one refuses it, and then something besides organization matters: speed, material, the way the parts hold together.

Therefore proves that many substrates will do, not that any will: the argument takes that step without justifying it.

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ObjectionAttacks the position Thought experimentThe Chinese Room — In the room the whole required organization is realized, and yet no one understands a word of Chinese: realizing the right program is therefore not enough to understand.
  1. In the room, everything functionalism asks for is assembled: the same inputs, the same intermediate states, the same outputs as a Chinese speaker. The organization is realized in full.
  2. Yet whoever applies the rules understands nothing: he does not even know what the sheets he hands back are about. He has the shape of the signs, never their meaning.
  3. If organization were what makes understanding, it would be there, present in the room. It is not.

Therefore So realizing the right organization is not enough to think: something is missing that the program, by construction, cannot supply.

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Argument Thought experimentThe Imitation Game — We never grant thought to others except on their words and gestures: to demand more of the machine is to apply a criterion we apply to no one.
  1. Of another's mind I have no direct access: I observe only conduct, words, reactions, and it is on that basis alone that I grant them an inner life.
  2. If, over a sustained exchange, nothing distinguishes a machine's answers from a person's, the criterion I use everywhere else is met.
  3. To deny it thought nonetheless presupposes a further criterion, one I require of none of my fellows and would be hard put to state.

Therefore So whatever realizes the conduct of a thinking being must be held to think: the substrate is no part of the criterion.

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Problems
  • Descriptive Thought experiment
    The Chinese Room

    Locked in a room, one answers flawlessly in Chinese by following a rulebook, without understanding a word: is running a program ever understanding, or only giving every sign of it?

    a mind that understands
  • Descriptive Thought experiment
    The imitation game

    If, in a blind conversation, nothing tells the machine from a person, must we grant it thought, or does passing for a mind never prove there is one?

    a conversation
  • Descriptive
    Intelligence without a body

    A program processes signs outside any world; but grasping a situation, acting with tact, may require a living body that inhabits it, which the disembodied machine lacks.

    a disembodied intelligence
  • Descriptive
    Does the substrate matter?

    If the exact organization of your brain were reproduced by a whole people passing messages, would that crowd really think, or do only certain materials yield a mind?

    the substrate of thought
  • Descriptive
    Thinking, or feeling

    Reasoning is one thing, feeling another: a machine might compute everything without there being "something it is like" to be it, thought with no consciousness at all.

    a machine's inner feel
  • PrescriptiveMoral
    Would we owe it anything?

    If a machine thought, would it have interests, a dignity, rights, or would it remain a thing we dispose of, owing it nothing?

    a thinking machine

Other positions on this axis: Only the living think · Not by program alone

Related axes: The enigma of consciousness · Nature of reality · Wholes and parts · Moral circle