In regard to Rene Descartes' Meditations, if there existed an all powerful evil demon, why couldn't it trick you into believing you exist?


If it is all powerful, why can't it trick you into thinking you exist and have thoughts?

If the cogito is unbreakable, then how could the demon be all powerful if it is bounded by laws it cannot break?


Posted 2014-08-20T11:23:30.573

Reputation: 89



You seem to be misunderstanding how Descartes handle the evil demon. He agrees with the force of your upper question:

If it is all powerful, why can't it trick you into thinking you exist and have thoughts?

But he then rejects this -- not on the grounds that "the cogito is unbreakable" but on the grounds that he feels compelled to assume there's a good God that makes it so that his inner faculties are not scrambled or deceived to such an extent that his project can never get moving. There's some circularity between Meditations 1, 2, and 3.


Med. 1 = I might be deceived in everything by an evil god including my belief that I am thinking Med. 2 = I exist as thinking thing [built on a dilemma between my belief I am thinking and the experience I have if I am deceived] Med. 3 = I have an idea of a good and perfect God that cannot come from me but instead must come from such a real being outside of me.

So Med.3's good God assumption is needed to kill the evil demon objection of Med 1. And Med 2. is needed to have the proof of a good God based on my inner ideas. [for a longer version, see here.]

Or to put it another way, the radical doubt attributed to "Descartes" really belongs to a boogie-man in the history of philosophy and Descartes engages in a slightly more pedestrian project that starts from the inner certainty of "clear and distinct ideas"


Posted 2014-08-20T11:23:30.573

Reputation: 23 970

+1 "Puisque je doute, je pense; puisque je pense, j'existe." - Antoine Léonard Thomas, 1765

– Chris Degnen – 2014-08-20T13:52:58.157

Although this is correct, I think you're skipping a crucial step here. – Chris Sunami supports Monica – 2014-08-20T13:56:12.260

@ChrisSunami I'm sure I'm skipping quite a few steps here, but which one do you think must be included to address the question? – virmaior – 2014-08-20T14:03:00.957

1Descartes must first establish that his own existence is secure, even in the case of the demon, before he can make the move of rejecting the demon. Although your answer accurately portrays a later stage of the Meditations, it does not provide Descartes' answer to the main question of the OP. – Chris Sunami supports Monica – 2014-08-20T14:08:49.690

I actually think Descartes's order of presentation differs from his order of argumentation. He leaves aside the possibility of an evil demon at the end of Med I. and only disproves it through his proof of God in Med III. But the proof in Med II only works if there's no evil demon -- otherwise it's possible that it's just scrambled junk. – virmaior – 2014-08-20T14:23:58.023

But if he bases his idea of God on a clear and distinct idea, why could an evil demon not create this idea? It is all powerful after all. – Ghozt12 – 2014-08-20T21:39:07.043

@user3381694 Descartes solves that by making the idea perfect -- and he knows he's not perfect and neither could an evil demon be. (The latter is because of a unity between goodness and perfection not shared by most contemporary philosophers). – virmaior – 2014-08-21T00:22:58.630

But perfection could just be a trick the demon has put in his mind? I mean he assumes that the demon could trick him about even fundamental truths such as geometry and mathematics. How does Descartes make the idea perfect, so perfect that an all powerful demon could not even trick him about it? – Ghozt12 – 2014-08-21T10:46:16.857

@user3381694 no, because perfection implies not tricking people (as I stated in my above comment) for the definition of perfect Descartes is using (this is a concept from Aristotle called the transcendental unity). -- Now, you can critique Descartes for believing that is true, but you can't fault him for consistency on this particular point. Perfection smuggles in goodness under this definition. – virmaior – 2014-08-21T12:31:59.810


Even if you are fooled, it implies there is some "you" that is being fooled. You might be mistaken as to all details of your existence. You might only exist as a momentary amusement of the malign being --some walled-off corner of its own consciousness perhaps --but even so, you have some form of existence.

This is a directly verifiable fact --the only such fact available to us, in Descartes' view. If you can think you exist, there is a you that exists capable of sustaining that thought.

For the second part of your question: Does this pose a challenge to the description of the malign being as "all powerful"? The answer depends on your concept of "all powerful". Descartes means that the being is capable of doing the physically impossible, not that it is capable of doing the logically impossible. If the malign being wants to create something capable of thought, logic compels it to grant that creature at least the bare minimum level of existence necessary to sustain thought.

Chris Sunami supports Monica

Posted 2014-08-20T11:23:30.573

Reputation: 23 641

You're missing the threat of the evil demon from Med I on this interpretation. Decartes admits that if such a demon exists, it's possible that there's not even a stable entity capable of anything including holding thoughts and doubting. – virmaior – 2014-08-20T14:25:04.723

I don't think either the outline you provided or the original text supports your claim. Yes, the thinking being may in fact be deceived about all things including the truths of mathematics and logic and the evidence of all senses, but it cannot be deceived about the fact that it itself exists (in at least the moment in which it is deceived). (Cogito 1 in your outline, Meditation II.3) – Chris Sunami supports Monica – 2014-08-20T14:37:00.447

On your interpretation, what does the evil demon passage mean in Med 1? – virmaior – 2014-08-20T15:38:06.090

It's just an introduction to the argument of Med. II. . He introduces the concept here, but makes no attempt to address it until Med II.

– Chris Sunami supports Monica – 2014-08-20T16:47:44.330

But @chris Sunami is the premise: if you are deceived, you exist (at least in that moment) a logical assertion. Ie. if a then b. Could the demon tricked you into thinking that. Another question, if God was all powerful, could he create something that did not exist? If not why is this law so powerful that not even an all powerful god can break it, why is logic unbreakable by a all powerful god/demon? – Ghozt12 – 2014-08-20T21:48:45.610

Wow I just realised what I am asking is the Omnipotence paradox, if anyone is interested. – Ghozt12 – 2014-08-20T22:01:21.957

Whether or not you find the Cogito persuasive depends on if you think the idea of something with absolutely no existence being fooled into thinking it has existence is anything other than just nonsense (in a technical sense). Remember, what Descartes is arguing for at this particular point is a very liberal definition of existence. The thinker doesn't need to persist, to be material, to be self-contained, to have any definite properties, it just needs to be "not nothing," and the not nothing it must at least be is the thought itself. – Chris Sunami supports Monica – 2014-08-21T15:28:24.040


The demon is not all-powerful

One power the demon lacks is the ability to cause me to believe that I exist if I do not. This must be so, since unless I exist I cannot be induced to believe anything. Also your question defeats itself: 'why can't it trick you into thinking you exist and have thoughts?' This assumes the existence of 'you' since something that does not exist or have thoughts cannot be 'tricked'. One can't trick the non-existent.

Given that the demon is not all-powerful, the second question (how is 'it is bounded by laws it cannot break?) does not arise.

Descartes' language

Descartes often ascribes omnipotens to God but in Med. 1 (1641) he says of the evil demon only that it is summe potens or potentissimus, which carry the sense of 'very or extremely powerful'. These Latin terms are sometimes (even often) used by Descartes in the sense of 'omnipotence' but it is unlikely that this is the sense here since (a) in the French translation (1647) Descartes leaves no room for doubt that 'omnipotence' is not meant, since he approves the rendering of summe potens as 'très' or 'extrêmement puissant', i.e. 'very or extremely powerful'; and (b) we know from Med. 2 the finitude of the evil demon's power. To repeat from above: The demon cannot get me to believe I exist and am thinking if I do not exist and am not thinking. The demon cannot perpetrate this illusion since ex hypothesi I do not exist and what does not exist cannot be deceived or illuded.

Geoffrey Thomas

Posted 2014-08-20T11:23:30.573

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If it is all powerful, why can't it trick you into thinking you exist and have thoughts?

We have to get clear on an equivocation in the word 'you' in this question. First of all, the Meditations are done in the first person, with the use of the word 'I'. But we have to note that the word 'I' when we are Meditating does not refer to the author of the Meditations on First Philosophy, but to whoever is doing the meditations. So when Descartes uses the word 'I' in that text, he is not referring to Rene Descartes, the physical person who lived in the 1600s. Rather, he is referring to the owner of the stream of thoughts of whoever is currently meditating.

This is an important quibble, because notice that the Evil Demon can trick you into thinking that you exist and have thoughts. That is, if by you we mean the actual physical person you are, with all of your contingent physical properties, memories, character traits, etc. So it is possible for Rene Descartes, when he is meditating, to be tricked about the existence of Rene Descartes. Why? Because everything Rene Descartes knows about himself is subject to the doubt of the Evil Demon. It may be that Rene Descartes doesn't actually have this body, doesn't actually live in Europe in the 1600s, indeed, that Rene Descartes was never born!

So when the Meditator famously says, "I am, I exist," this doesn't prove the existence of Rene Descartes, it proves the existence only of the "owner of the present stream of thoughts, whoever (or whatever) that is"!

The logical limit of this power to deceive would have to be found in the Cogito, then, not as a psychological person but as a "pure I". In order for the demon to be logically able to carry out his malicious task, the demon must work with the structure of the Cogito:

I think about [x].

That is, the logical structure of deception (or, if you prefer, of misrepresentation) is that there must be something about which someone is being deceived (or something that is being misrepresented). The demon can only misrepresent by varying what he puts inside the [x]. Hence, the demon cannot dispose with the structure of 'I think about [x]' and still carry out his epistemic hostility.

This is why the Meditator cannot be deceived about "his" existence--but only his existence as this pure I. Hence it still may be that all my memories are deceptive, that my name is not Rene Descartes after all, etc. What we have is a structure of aboutness or of representation. All the pure I can confirm about itself in this epistemic environment is that there is something about which it has impressions, that is, that there is a spontaneous image there that purports to be about something. No aboutness, no possibility of deception.

This, incidentally, is why Descartes separates psychophysical existence from the existence of the pure I in Meditations 2 and 6. The structure of aboutness does not by itself guarantee the psychophysical predicates of the I. Any predicates of the I would have to be obtained from inside the [x]. Thus before psychophysical predicates can be attributed to the I, a structure of veridicality must be in place (a measure of the representation inside the [x] against an independent norm). Descartes famously (and to many students' disappointment) posits God as the independent norm from which he obtains veridical representation and therefore recovers psychophysical predicates, preserving his science of mechanics.


Posted 2014-08-20T11:23:30.573

Reputation: 1 931


An act of a consciousness has no, in principle, such a property as ownership: all mental events - thoughts, senses, intentions etc appear without special labels indicating that they are mine, your, his (no description of any mental event necessitates such an indication). The ownership is somehow declared itself by the fact that they are all integrated together with over events in some particular (my, your, his) consciousness. This is we who put this label "my thought" on them and they become our thoughts.

If the demon could cheat with labels - he could trick you. But no labels - no cheating. This means that if he could produce somehow in you an act of thought and you realize that it is your thought - OK, it would indeed be your thought, because your declaration is enough for it. Here the demon trick fails.

Gelato di Cræma

Posted 2014-08-20T11:23:30.573

Reputation: 339

You've lost me completely in your second paragraph with the "your declaration is enough for it" bit. – virmaior – 2014-08-21T23:30:09.240

May be it is trivial that I try to explain but I could say it in another way: the demon can cheat with external things and their intrinsic properties trying to demonstrate something which is not in them. The fact that any mental event is mine is not the intrinsic property of this event. It is just a constatation - I understand that this event is a part of my current experience. I do not find the fact that this event is mine - it is not its special property. It is enough to me to understand that it is mine in order that it becomes mine really. Therefore any cheating of the demon stops here. – Gelato di Cræma – 2014-08-22T10:28:13.303