QuestionsIs the mind the brain?The flying man: the soul knows itself without the body
Is the mind the brain?The mind is not matter

The flying man: the soul knows itself without the body

The flying man

Avicenna c. 980 · c. 1037The soul knows it exists before any body: the flying man.
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What it claims

His self, his "I", is something other than his body and organs: the soul is not the body, and indeed is not a body.

Why

Deprived of all sensation, the flying man is still sure he exists without affirming his body: so the self is not the body.

The same idea through history
Avicenna1027Three versions: at the beginning and end of On the Soul in the Shifa', then in Pointers and Reminders, where he also answers the objection "I know myself through my acts".
René Descartes1641I can doubt that I have a body, not that I exist as a thinking thing: so I am a thinking thing, distinct from the body. The comparison with the flying man is long-standing; a direct influence is not proven.
In short

"The flying man: the soul knows itself without the body" is an argument by Avicenna (The Book of Healing, On the Soul, I, 1 and V, 7; Pointers and Reminders, namat 3, 1027) on the question "Is the mind the brain?" (answer: the mind is not matter). Its claim: His self, his "I", is something other than his body and organs: the soul is not the body, and indeed is not a body. According to AskPhilosophy's logic check (Z3 solver), the conclusion does follow from its 3 premises. AskPhilosophy presents 4 objections, 2 of them with a documented reply, and the original text behind each premise, checked word for word.

The Book of Healing, On the Soul, I, 1 and V, 7; Pointers and Reminders, namat 3
Valid

Imagine a man created all at once, fully grown, his eyes veiled, floating in the air without touching anything, his limbs spread apart. He sees nothing, feels nothing, not even his own body. Does he know that he exists? Yes, Avicenna answers, without any doubt. Yet he knows nothing of his hands, his heart or his brain. Six centuries later Descartes would make a very similar argument; we do not know whether he knew Avicenna's text, which had circulated in Latin since the 12th century. Avicenna himself presents the flying man as an "awakening" for those able to see, not as a formal demonstration.

P1The flying man, deprived of all sensation, is still certain that he exists: he affirms his own self without the slightest doubt.
P2At the same time, he affirms the existence of no part of his body: not his limbs, nor his entrails, nor his heart, nor his brain, nor anything outside.
P3What is affirmed is something other than what is not affirmed: one and the same thing cannot be both known and unknown.
Therefore his self, his "I", is something other than his body and organs: the soul is not the body, and indeed is not a 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.
The form is valid, with no hidden premise. The computer even shows that P3 is not needed: in logic, if one thing has a property and another lacks it, they must be different (this is "Leibniz's law": identical things share all their properties). So the whole debate lies elsewhere: is "being affirmed by the flying man" a real property of the thing, or only a way in which he knows it? I can know someone under one name and be ignorant of him under another, without there being two people. If "being affirmed" depends only on what I know, P1 and P2 do not allow the conclusion. Avicenna was aware of this: he presents the flying man as an "awakening" meant for those able to see, and gives elsewhere (On the Soul, V, 2) a more technical demonstration that the soul is immaterial.
Analogy. With your eyes closed, in a sensory deprivation tank, you no longer feel your arms or legs. Yet you know perfectly well that you are there. Avicenna concludes that this "you" is not made of arms and legs. His critics reply: perhaps it is, and you simply no longer feel it.

Objections

4

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

Objection anticipated by Avicenna (Pointers and Reminders) 1032 · attacks premise 1

I do not know myself directly: I know myself through my acts. I know I exist because I think, I move, I do something.

Avicenne replies
Avicenne
In the imagined situation you have no act and no movement to observe. And if you recognise an act as "your" act, you already knew yourself: your self is part of the meaning of "your act". It is known before the act, or at least with it, but not through it.
Arnauld, against Descartes 1641 · attacks premise 3

I can clearly conceive a right triangle without knowing that the square on the hypotenuse equals the sum of the squares on the sides; yet that property belongs to it. Knowing one thing without knowing another does not prove they are separate: my knowledge may simply be incomplete. The objection targets Descartes, but it hits the flying man in the same way: being unaware of one's brain does not prove that the self is not the brain.

no reply
No reply possible: objection raised in 1641, after the author's death (1037).
The debate goes on (our summary) Avicenna could not answer Arnauld, who came six centuries after him. But he himself offers two elements. First, he presents the flying man as an "awakening", not as a complete proof. Second, at the end of On the Soul, he insists that what is unknown cannot be the same as what is known, and that our limbs are to us like clothes. His defenders add that the self is not known through an incomplete description, but wholly and directly. His critics answer that this is exactly what would need proving. (Our summary.)
Hume 1739 · attacks premise 1

When I enter into myself, I always stumble on some particular perception: heat, cold, pleasure, pain. I never catch myself without a perception. So the flying man, deprived of all perception, would find nothing in himself; and in deep sleep we are not even aware of ourselves.

Avicenne replies
Avicenne
Whoever sees clearly never forgets that he exists. Even the sleeper in his sleep and the drunkard in his drunkenness do not lose sight of their self, even if their representation of it does not stay in their memory.
The debate goes on (our summary) This passage was written seven centuries before Hume: it answers his argument from sleep, but not his central observation, namely that when we observe ourselves we never find a bare "self", only perceptions. Each asserts the opposite of the other about what introspection reveals, and neither can prove his testimony to the other. (Our summary.)
N
Neuroscience (20th-21st centuries) 1990 · attacks the conclusion

Self-awareness depends on the brain: anaesthesia suspends it, some lesions alter it deeply (losing the sense of inhabiting one's body, of recognising one's limbs as one's own). That the flying man does not feel his brain does not show that his self exists without it: we never feel our brain, even when it is working.

no reply
summary: their text is not yet in our corpus
No reply possible: objection raised in 1990, after the author's death (1037).
The debate goes on (our summary) Avicenna already knew that imagination, memory and estimation are seated in the brain (On the Soul, I, 5). He held the organs to be instruments of the soul: damaging the instrument hinders the action, without showing that the instrument is what acts. His critics answer that the more thought is explained by the brain, the less useful this hypothesis of a hidden user becomes. The debate remains open. (Our summary.)