QuestionsIs the mind the brain?The brain is the nail, thought is the coat
Is the mind the brain?The mind is not matter

The brain is the nail, thought is the coat

The coat and the nail; the brain as organ of attention to life

Henri Bergson 1859 · 1941The free act springs from our whole personality: lived duration cannot be cut up like space.
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What it claims

The life of the mind cannot be an effect of the life of the body: everything happens as if the body were simply used by the mind, and nothing proves the two to be inseparable.

Why

The brain holds and draws only a small part of thought: it serves to act and to recall, not to produce or store the mind.

The same idea through history
René Descartes1641Descartes separates the soul from the body through pure thought. Bergson does not start from a definition of the soul but from the facts: brain lesions, diseases of memory.
Henri Bergson1896In Matter and Memory, Bergson holds that the body is one image among others and cannot contain memories: perceptions "are not in it; it is in them".
Henri Bergson1912In the lecture "The Soul and the Body" (reprinted in Mind-Energy, 1919), he gives the thesis in plain terms: the coat, the nail, the conductor.
In short

"The brain is the nail, thought is the coat" is an argument by Henri Bergson (Matter and Memory, 1896; "The Soul and the Body", 1912, 1896) on the question "Is the mind the brain?" (answer: the mind is not matter). Its claim: The life of the mind cannot be an effect of the life of the body: everything happens as if the body were simply used by the mind, and nothing proves the two to be inseparable. According to AskPhilosophy's logic check (Z3 solver), the argument is valid only if one grants a premise the author leaves unstated (P5, P6). AskPhilosophy presents 3 objections, 2 of them with a documented reply, and the original text behind each premise, checked word for word.

Matter and Memory, 1896; "The Soul and the Body", 1912
Valid with an implicit premise

When you are hit on the head you lose consciousness; a drug changes your mood; a lesion makes you lose a word. People often conclude: thought is nothing but brain. Bergson replies that these facts only prove that the two are linked. A coat falls if you pull out the nail it hangs from, but the nail is not the coat. He holds that the life of the mind overflows the life of the brain on every side, and that the brain mainly serves to prepare action and to recall memories. This is not a thesis about a hidden soul: he builds it on the study of the diseases of memory in his time. It does not prove that the mind exists without the brain. It says that nothing shows the mind to be its product, and that many facts suggest the opposite; at the end of his lecture, Bergson concludes only that a survival of the mind, for a time, becomes possible and even probable.

P1Experience shows only that the life of consciousness is tied to that of the body: a solidarity, nothing more. A coat is tied to its nail without being its effect or its equivalent.
P2The brain does not determine thought: one could guess the brain state from the state of mind, but not the reverse, since the same brain state fits a multitude of states of mind, as one frame fits many pictures.
P3The brain is turned toward action: it prepares gestures, the nascent movements of thought, and selects what follows. It is "the organ of attention to life", not the organ of thought.
P4Memories are not kept in the brain: in diseases of memory, an emotion can suddenly bring back a memory thought lost. The brain serves to recall memory, not to keep it.
P5 · implicit premiseIf the life of the mind were only an effect of the life of the body, the brain would have to determine thought and contain memories.
P6 · implicit premiseIf the mind is not an effect of the body, is tied to it and the body serves it as an organ of action, the best explanation is that the body is used by the mind.
Therefore the life of the mind cannot be an effect of the life of the body: everything happens as if the body were simply used by the mind, and nothing proves the two to be inseparable.

click a premise to reject it

If you accept every premise, logic forces you to accept the conclusion. So the debate is about the premises.
Checked by a logic solver: the premises cannot all be true while the conclusion is false.
Without the implicit premise: Without P5, one can accept P2 and P4 and say the brain does produce thought, but in a subtler way than simple storage: through processes we do not yet understand. Without P6, one can stay at "neither": the mind is not a simple effect of the brain without being a reality that uses it.
The argument is valid with the hidden premises P5 and P6. P5 states what a mind "produced" by the brain would imply; P2 and P4 show this is not so; P6 moves from "not an effect" to "used by the mind", which is a best explanation rather than a proof. P1 and P3 give the facts on which P6 rests.
Analogy. The conductor waves his baton: the gestures follow the symphony and make it possible, but the orchestra plays far more than a baton shows. Someone who saw only the baton would know little of the music. For Bergson, the brain is that baton: it mimes and directs the mind, it does not contain it.

Objections

3

Each objection is a conversation: click to see who replies and where the debate stands.

F
Francis Crick 1994 · attacks the conclusion

In The Astonishing Hypothesis, Crick holds that our joys, our memories and our sense of being a person are nothing more than the activity of a vast assembly of nerve cells and their molecules. Consciousness would then be fully explained by the brain.

Bergson replies
B
Bergsonian reply
Bergson answered this kind of thesis in advance: observation and science let us affirm only a certain relation between brain and consciousness. Moving from relation to identity is not a scientific conclusion but a philosophical choice.
Where the debate stands (our summary)Core disagreement: do ever finer correlations between brain and experience prove identity (Crick) or only a relation (Bergson)? Both camps read the same facts.
E
Eric Kandel 2001 · attacks premise 4

The molecular biology of memory shows that learning durably changes synapses, and even the expression of certain genes, in Aplysia (a sea slug) and then in mammals. Memories would therefore be stored in the brain after all, as material changes.

Bergson replies
B
Bergsonian reply
Bergson distinguishes two memories: that of motor mechanisms, kept in the body as habit, and that of personal memories, dated images of the past. Changes in synapses prove the first. They do not prove that image-memories are deposited in matter.
X
Xu Liu, Steve Ramirez, Susumu Tonegawa 2012
Summary: in mice, Tonegawa's team tagged the hippocampal neurons active during fear learning, then reactivated them with light. The animal showed fear in a place where nothing had caused it. For them, these neurons form a trace ("engram") that suffices to recall a specific memory.
Where the debate stands (our summary)Open point: does reactivating neurons make a memory reappear (it is in them) or merely recall it (they serve to retrieve it)? Current experiments have not decided between the two readings.
J
Jaegwon Kim 1998 · attacks premise 6

Kim objects, against any dualism, that if the mind is something other than the brain but acts on the body, we must say how: yet every bodily movement already has a complete physical cause. A distinct mental cause would be redundant (the "causal exclusion problem").

no reply
No reply possible: objection raised in 1998, after the author's death (1941).
The debate goes on (our summary) Bergson died in 1941, before this objection. A Bergsonian would answer that the brain does not do all the work: it "mimes" thought and makes it enter action. Bergson speaks of the brain as the "point of insertion of the mind in matter" without explaining how this insertion happens.
Where the debate stands (our summary)Open point: Bergson describes the link between mind and body but does not explain how the mind would act on matter. This is the classic difficulty of any dualism.