QuestionsIs the mind the brain?The mind is born, ages and suffers with the body: it is material and mortal
Is the mind the brain?The mind comes from matter

The mind is born, ages and suffers with the body: it is material and mortal

Lucretius' proofs that the soul is mortal; "the mind is a part of man"

Lucrèce c. 99 BC · c. 55 BCAtoms swerve slightly by chance (the clinamen): this is what makes the will free.
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What it claims

The mind is a material thing, a part of man, and it is mortal: it does not survive the dissolution of the body.

Why

The mind grows, ages, falls ill, gets drunk and is cured along with the body, and moves limbs only by contact: so it is corporeal.

The same idea through history
Democritus420 BCDemocritus already made the soul an assembly of atoms. Epicurus, then Lucretius, took up this physics and added proofs drawn from the experience of the body.
Lucrèce55 BCLucretius, in book III of his poem, places the mind in the chest and makes it a part of man, made of very fine atoms. He multiplies proofs from facts: childhood, old age, illness, wine, remedies.
In short

"The mind is born, ages and suffers with the body: it is material and mortal" is an argument by Lucrèce (On the Nature of Things, III, 94-135, 161-176, 445-529, 55 BC) on the question "Is the mind the brain?" (answer: the mind comes from matter). Its claim: The mind is a material thing, a part of man, and it is mortal: it does not survive the dissolution of the body. According to AskPhilosophy's logic check (Z3 solver), the argument is valid only if one grants a premise the author leaves unstated (P7). AskPhilosophy presents 3 objections, 1 of them with a documented reply, and the original text behind each premise, checked word for word.

On the Nature of Things, III, 94-135, 161-176, 445-529
Valid with an implicit premise

For many people thinking would be the work of a separate soul that lives in the body like a tenant. Lucretius, a Latin poet and a follower of Epicurus, answers with facts anyone can check. The mind, he says, is a part of man like the hand or the eye. It is born with the body, it is weak in a child and falters in an old man. Illness disturbs it, wine intoxicates it, a medicine cures it. And it moves the body, which only a bodily thing can do. What changes with the body in this way is material, and therefore mortal. He writes this around 55 BC to cure the fear of death (see the argument on death, lucrece-symetrie). The Latin text is in our corpus; the French is Nisard's translation (1868), free, and the English an old verse translation whose divisions differ.

P1The mind, seat of judgement and guide of life, is a part of man, just as the hand, the foot and the eyes are parts of the living being.
P2The mind is born with the body, grows with it and ages with it: weak in the child, stronger in maturity, it falters when the body is broken by the years.
P3Illness of the body leads the mind astray, and wine disturbs it: it is struck by the same causes as the body.
P4The mind is cured like the sick body: remedies can heal it.
P5The mind moves the limbs, wakes the body from sleep, changes the face; but none of this happens without touch, and nothing touches without a body. So the mind is of a corporeal nature.
P6What is immortal suffers neither rearrangement, nor increase, nor loss of parts: whatever leaves its own bounds dies to what it was.
P7 · implicit premiseWhat is born, grows, ages, falls ill and is cured with the body, and whose state is changed by acting on the body, has parts that can be added, rearranged or removed.
Therefore the mind is a material thing, a part of man, and it is mortal: it does not survive the dissolution of the body.

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 P7, one can accept all the facts and still say that the mind is of another nature: a pianist plays badly on an out-of-tune piano without his music being a part of the piano. The mind would depend on the body as a musician on his instrument, without being identical with it, and could outlive the instrument.
The argument is valid with the hidden premise P7. P2, P3 and P4 describe facts; P7 says that such facts imply a mind that can be altered through its parts; P6 says that the immortal cannot; so the mind is not immortal. P5 establishes separately that it is corporeal. The objections target P7: a thing can depend on the body without being identical with it (Bergson), or command the body (Plato), or be of another nature (Descartes). Note that Lucretius himself distinguishes the mind (animus) from the soul (anima), two parts of one substance.
Analogy. A flame depends on its candle: it grows when the wax is plentiful, flickers in the wind, sinks when the wick wears out, and goes out with it. No one imagines it could burn alone in the air after the candle. Lucretius sees the mind this way.

Objections

3

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

Plato 360 BC · attacks premise 7

In the Phaedo, Socrates refuses that the soul be a mere harmony of the body, like the tuning of a lyre. If it were, it could only follow the states of the body. But it does the opposite: it resists the body's desires, for example it holds one back from drinking when the body is thirsty. What commands the body is therefore not reducible to what the body gives it.

Lucrèce replies
L
Lucretius 55 BC
Lucretius also rejects the harmony theory: he tells the Greeks to keep the word. For him, mind and soul make one substance, and the mind, which he also calls intelligence, is as it were its head and rules over the whole body.
The debate goes on (our summary) Our summary: Lucretius thus admits that the mind commands the body, but holds it to be a material part of the living being. Plato would answer that commanding and resisting matter shows another nature. The debate is about what follows from "commanding": one part of the body can also govern others, as a chief governs his army.
Where the debate stands (our summary)Our summary: an open point. Plato and Lucretius agree against the harmony theory, not on the conclusion. Today materialists say the brain commands the rest of the body, and their opponents say that does not explain thought.
Henri Bergson 1912 · attacks premise 7

In "The Soul and the Body", Bergson grants that the life of consciousness is bound to the life of the body, that there is solidarity between them, nothing more. He compares consciousness to a coat hung on a nail: the coat falls if the nail is pulled out, it tears if the nail is sharp, without the nail being the coat. Showing that the mind depends on the brain does not prove that it is the brain.

no reply
No reply possible: objection raised in 1912, after the author's death (-55).
The debate goes on (our summary) Our summary: Lucretius died nearly two thousand years earlier, but his argument is not only dependence: P5 (the mind acts by contact) and P6 (the immortal does not change parts) target the nature of the mind, not only its solidarity with the body. A defender would also say that the precision of the links between lesions and losses (language, memory) is what identity predicts. Bergson treats that point for the memory of words in the same lecture.
Where the debate stands (our summary)Our summary: a deep, open disagreement. Dependence is granted by all; the disagreement is about what it proves. Neither reading is judged decisive.
René Descartes 1641 · attacks the conclusion

In the Sixth Meditation, Descartes has a clear and distinct idea of himself as a thinking, unextended thing, and a distinct idea of body as an extended, unthinking thing. He concludes that his soul is entirely and truly distinct from his body, and can exist without it. He nevertheless grants that it is very closely conjoined with it, which accounts for the effects Lucretius lists.

no reply
see the argument
No reply possible: objection raised in 1641, after the author's death (-55).
The debate goes on (our summary) Our summary: Lucretius does not know this argument, born sixteen centuries later. A Lucretian would answer that a clear idea of oneself does not prove the mind can exist without a body, and would recall the facts of dependence from P2 to P4. Critics of Descartes have also noted that one can conceive things that cannot exist separately.
Where the debate stands (our summary)Our summary: a disagreement at the starting point. Descartes starts from what the mind conceives clearly, Lucretius from what experience shows. Dualism is still defended today (see Descartes' argument), and so is materialism.