QuestionsIs the world real?An illusion that nothing could reveal is no illusion: the evil genius's world is our real world
Is the world real?Virtual is real too

An illusion that nothing could reveal is no illusion: the evil genius's world is our real world

Bouwsma's reply to the evil genius

O. K. Bouwsma 1898 · 1978The evil genius deceives no one: an illusion that nothing could ever reveal is no illusion.
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What it claims

The evil genius has created his own illusions without being deceived himself, and no one else has been deceived either. The possibility of a "false" but identical world does not show that we are deceived: the world we see is the real one.

Why

We use the word "illusion" only for what can be discovered: a deception that none of our senses could detect deceives no one.

The same idea through history
René Descartes1641Descartes imagines an evil genius who makes everything seem to exist as it does now when nothing exists. Bouwsma examines what such a deception would mean, and concludes that no one is deceived.
O. K. Bouwsma1949Bouwsma (1949) uses the example of paper flowers to show that illusion supposes a possible way of finding it out. It is the classic source of the "veridicalist" reply to scepticism, on which our beliefs remain true in the evil genius's world.
In short

"An illusion that nothing could reveal is no illusion: the evil genius's world is our real world" is an argument by O. K. Bouwsma ("Descartes' Evil Genius", The Philosophical Review 58 (1949), pp. 141-151, 1949) on the question "Is the world real?" (answer: virtual is real too). Its claim: The evil genius has created his own illusions without being deceived himself, and no one else has been deceived either. The possibility of a "false" but identical world does not show that we are deceived: the world we see is the real one. According to AskPhilosophy's logic check (Z3 solver), the argument is valid only if one grants a premise the author leaves unstated (P4). AskPhilosophy presents 3 objections, 1 of them with a documented reply, and the original text behind each premise, checked word for word.

"Descartes' Evil Genius", The Philosophical Review 58 (1949), pp. 141-151
Valid with an implicit premise

Descartes imagines a very powerful evil genius who deceives us about the sky, the earth, colours and all external things. Bouwsma takes the boast seriously and asks what such a deception would be. If the genius turns the flowers into paper, we can find it out: that is indeed an illusion. But if he makes the trick so perfect that nothing could give it away, then an illusion that neither sight, touch nor smell can detect, he says, is not an illusion in the sense in which we use the word. The genius himself sees it through a sense that men do not have. So he has created his illusions without either he or anyone else being deceived. Our reading, which is that of the "veridicalists" after him: the genius's world is then our real world.

P1The evil genius is supposed to deceive us in such a way that neither sight, nor touch, nor smell can detect the illusion.
P2An illusion supposes the possibility of discovery: if the genius changes the flowers into paper, we can find out and know it is an illusion. A deception that could never be found out would be no illusion, at least in the sense in which we use the word.
P3Human beings do not use the word "illusion" in relation to a sense that only the evil genius possesses. The genius sees the illusion he made, but that does not make it an illusion for us.
P4 · implicit premiseTo be deceived about the world is to be the victim of an illusion in the sense in which we use that word.
Therefore the evil genius has created his own illusions without being deceived himself, and no one else has been deceived either. The possibility of a "false" but identical world does not show that we are deceived: the world we see is the real one.

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 P4, the computer finds a case where there is no illusion in the ordinary sense of the word, and yet someone is deceived: for instance because he believes false things about the world without anyone being able ever to show him.
The argument is valid with the hidden premise P4. The genius is supposed to deceive undetectably (P1). But an illusion must be discoverable (P2), in the sense in which we use the word (P3). So an undetectable deception is not an illusion. Since being deceived is being the victim of an illusion (P4), no one is deceived. Objections target P2 (can we speak of an undiscoverable illusion?) and P4 (can one be deceived without the word "illusion" applying?).
Analogy. If I say a chess game was rigged in a way that no one, however hard they look, could see, I am asked what "rigged" still means. Bouwsma thinks the word "illusion" loses its meaning in the same way when every possibility of discovering it is removed.

Objections

3

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

René Descartes 1641 · attacks the conclusion

Suppose a very powerful and cunning genius has employed all his artifice to deceive me: the sky, the air, the earth, colours, figures, sounds and all external things would be nothing better than illusions and dreams.

Bouwsma replies
see the argument
O. K. Bouwsma 1949 · Bouwsma, on the genius's deception
Bouwsma sums up his article this way: he tried to understand the genius's claim to deceive about the sky, the earth, colours and external things, asking what such deceptions and such illusions would be. He concludes that the genius has created his own illusions without having been deceived himself, and that no one else has been deceived either.
The debate goes on (our summary) Our summary: Bouwsma answers Descartes on the meaning of his words, not on his logic. For Bouwsma, the Cartesian supposition holds only if the word "illusion" keeps a meaning that the genius, and he alone, could understand.
Where the debate stands (our summary)Our summary: the disagreement is old and open. For Descartes, a hypothesis is intelligible as soon as it does not contradict itself. For Bouwsma, it must also be statable with the words we have.
David Chalmers 2018 · attacks premise 2

Chalmers is sympathetic to a "veridicalist" reply, but thinks Bouwsma's argument does not succeed. Even in ordinary language, we can make perfect sense of the idea of an undiscoverable illusion: we speak without difficulty of what can never be known. Bouwsma's idea, that illusion supposes the possibility of discovery, is therefore not imposed by the use of the word.

no reply
No reply possible: objection raised in 2018, after the author's death (1978).
The debate goes on (our summary) Our summary: Bouwsma died in 1978 and could not reply. Chalmers tries to keep the conclusion (our beliefs are largely true in the genius's world) by another route, structuralism.
Where the debate stands (our summary)Our summary: an open point. Philosophers who defend Bouwsma's idea rely on language use, others on verification or coherence, and others abandon it.
David Chalmers (the third-person case) 2018 · attacks the conclusion

By Bouwsma's lights, the hypothesis "my experiences are produced by a demon" seems hard to hold true, since there is no first-person evidence for it. But for someone else, we might have good evidence that a third party produces their experiences. This risks an odd asymmetry: "they are the victim of a demon" would be true, "I am the victim of a demon" false. The argument slides from "no one is deceived" to "the hypothesis makes no sense".

no reply
No reply possible: objection raised in 2018, after the author's death (1978).
The debate goes on (our summary) Our summary: Bouwsma (who died in 1978) considers only two points of view, that of the deceived humans and that of the genius, who sees the illusion through a sense humans lack. He says nothing of a human observer placed outside.
Where the debate stands (our summary)Our summary: an open point. It is debated whether the first-person and third-person evil-genius scenarios should be treated alike.