Does Descartes reason in a circle when he argues that everything we clearly and distinctly perceive is true because God exists and is not a deceiver?


No he does not.   Despite the popular claim that Descartes uses his "clear and distinct perceptions"to prove the existence of a non-deceiving God, and then uses the existence of a non-deceiving God to prove that his "clear and distinct perceptions"are true, he does not in fact do this.

Descartes uses the description of a "clear and distinct perception"for what we would now call an "intuitive awareness of a self-evident truth".   He concludes that having such an intuition is adequate evidence to make a belief reasonable and probable.   But he does not, before his proof of the existence of God as a non-deceiver, use only that rationale for concluding that such intuitions are "certain".   He supplements the reasonability conclusion with a claim that some of these clear and distinct perceptions are also immune from doubt -- they are what we would now call "logically necessary truths".   And it is upon this latter category of clear and distinct perceptions that he bases his proof that God exists as an omni-benevolent entity.   Only then does he conclude that God would not deceive him about his clear and distinct perceptions, and that therefore he can treat those intuitions as also being necessarily true.

In Meditation I and Meditation II, Descartes sets about his program of "Methodic Doubt"in order to establish an absolutely certain foundation for his knowledge.   He determines to dismiss as insufficiently certain any items of knowledge that he can find some reason to doubt.   To that end, he proceeds through the major classifications of knowledge, and dismisses as unacceptably dubitable all his former claims to knowledge, except one.   As an aid in this process, he imagines a deceiving god or demon who intends to systematically deceive him about things.   But his omnipotent deceiver is specifically limited -- while the deceiver can fool him about what his senses report to him, and can fool him about what his memory reports to him, it cannot deceive him about what his thinking, his reason, his understanding, reports to him.

Descartes claims a faculty that he variously calls "intuition", the "natural light", the "light of nature", and the "light of reason"that he considers provides him with information that is beyond doubt, information that is proof against the deceptions of the deceiving god/demon.

"By ‘intuition'I do not mean the fluctuating testimony of the senses or the deceptive judgement of the imagination as it botches things together, but the conception of a clear and attentive mind, which is so easy and distinct that there can be no room for doubt about that we are understanding.   Alternatively, and this comes to the same thing, intuition is the indubitable conception of a clear and attentive mind which proceeds solely from the light of reason."     AT: Vol X, Pg 368 -- Principles

This is a far higher degree of epistemic warrant than he accepts for "clear and distinct perceptions".   At the start of Meditation III, Descartes claims that an omnipotent god (at this point, Descartes is talking about a generic "god", not the "God"whose existence he intends to demonstrate) could even cause him to err in whatever it is that he clearly and distinctly perceives.   Yet Descartes also notes that even if this god is a deceiver, a deceiver can never bring it about that Descartes can be deceived into believing a manifest contradiction.   Descartes is clearly distinguishing between a "run of the mill"clear and distinct perception and an intuition of a logically necessary truth (one that cannot involve a "manifest contradiction").

"But as often as this preconceived opinion of the sovereign power of a God presents itself to my mind, I am constrained to admit that it is easy for him, if he wishes it, to cause me to err, even in matters where I think I possess the highest evidence; and, on the other hand, as often as I direct my attention to things which I think I apprehend with great clearness, I am so persuaded of their truth that I naturally break out into expressions such as these: Deceive me who may, no one will yet ever be able to bring it about that I am not, so long as I shall be conscious that I am, or at any future time cause it to be true that I have never been, it being now true that I am, or make two and three more or less than five, in supposing which, and other like absurdities, I discover a manifest contradiction."
          Descartes / Vetch, Pg 235 -- Meditation III

This is the distinction that causes Markie to proclaim -

"Descartes'claim [to certainty] has two parts: (1) He has evidence for these beliefs that makes them very reasonable, and (2) that evidence resists even the slightest, most exaggerated reasons for doubt, so that his beliefs are certainties."     Markie, Pg 155

Clear and distinct perceptions are reasonable to believe, but can be challenged by the deceptions of a deceiving god/demon.

"My habitual opinions keep coming back, and, despite my wishes, they capture my belief, which is at it were bound over to them as a result of long occupation and the law of custom.   I shall never get out of the habit of confidently assenting to these opinions, so long as I suppose them to be what they are, namely highly probable opinions -- opinions which, despite the fact that they are in a sense doubtful, as has just been shown, it is still much more reasonable to believe than to deny."     AT: Vol VII, Pg 22 - Meditation II

But there are clear and distinct perceptions that are proof against the deceiving god/demon either because they are logically necessary (their being false would involve a manifest contradiction), or because they would remain true even if there was a deceiving god/demon at work.

"[. . .] for what the natural light shows to be true can be in no degree doubtful, as, for example, that I am because I doubt, and other truths of the like kind;"
          Descartes / Vetch, Pg 237 -- Meditation III

Using his Method of Doubt, by the start of Meditation III, Descartes has systematically examined all his beliefs and set aside those which he could call into doubt.   He finds only one belief which he can not doubt -- that the god/demon seeking to deceive him can not deceive him into thinking that he does not exist when in fact he does exist.  

"But there is a deceiver of supreme poser and cunning who is deliberately and constantly deceiving me; and let him deceive me as much as he can, he will never bring it about that I am nothing so long as I think that I am something."     AT: Vol VII, Pg 25 - Meditation II

In his effort to demonstrate that God exists, therefore, he can draw upon nothing beyond the thoughts ("ideas") that he thinks.   These alone are immune from the deceptions of the deceiving god/demon.

"Now, with respect to ideas, if these are considered only in themselves, and are not referred to any object beyond them, they cannot, properly speaking, be false;"Vetch, Pg 236 -- Meditation III

With this limited foundation, then, Descartes begins his proof by defining some classification schemes for his ideas.   At this point, Descartes is working strictly within his thoughts, and his reasoning ability -- an ability that the deceiver has no access to.  

"Nor do I refer to matters of faith, or to the conduct of life, but only to what regards speculative truths, and such as are known by means of the natural light alone."
          Descartes / Vetch, Pg 217 -- Synopsis of the Meditations

He observes that his thoughts, his ideas, when considered only as ideas, fall into three different classes.  

"But among these ideas, some appear to me to be innate, others adventitious [that is to be caused by things outside of me], and others to be made by myself (factitious);"Vetch, Pg 237 -- Meditation III

Although he, at this point admits that he has "not yet clearly discovered their true origin".

Descartes next sets up the distinction between "objective reality"and "formal reality".   He incorporates into them the Aristotelian / Scholastic notion of final or teleological cause.   Notice that here, unlike with the intuitive awareness of the Cogito ("I think, therefore I am"), Descartes does not invest any time in demonstrating that this truth, "manifest by the natural light,"is indeed immune to the deceptions of the deceiving god/demon.   Descartes is establishing this teleological principle by fiat -- he claims that the principle is a logically necessary truth.  

"Now, it is manifest by the natural light that there must at least be as much reality in the efficient and total cause as in its effect; for whence can the effect draw its reality if not from its cause ? And how could the cause communicate to it this reality unless it possessed it in itself ? And hence it follows, not only that what is cannot be produced by what is not, but likewise that the more perfect, in other words, that which contains in itself more reality, cannot be the effect of the less perfect; and this is not only evidently true of those effects, whose reality is actual or formal, but likewise of ideas, whose reality is only considered as objective."
          Descartes / Vetch, Pg 239 -- Meditation III

A thing (particularly, an Idea) has "objective reality"in virtue of representing something else.   Descartes originally posits the concept of objective and formal reality as a way to explain the difference between an object in the real world, and the idea of that object in our minds.   But at this point in his reasoning, he applies the classification only to the ideas of his mind.   According to Descartes, the amount of objective reality an idea has is determined solely on the basis of the amount of formal reality contained in the thing being represented.   "Formal reality"is simply the reality that something possesses in virtue of existing.   Formal reality is what he takes to be the cause of his ideas, while the ideas in themselves represent objective reality.  

Descartes then applies his classifications of ideas to his notion of "substance".   Since he believed that modes of substances (properties) were accidental modes of the underlying substance, he argues that the underlying substance has more "objective reality"than the modes.   His reasoning is that the underlying substance itself must be "more perfect"than could be any variations of that substance that are the modes we observe.   Again, this is a premise he establishes as beyond doubt.

"For, without doubt, those [ideas] that represent substances are something more, and contain in themselves, so to speak, more objective reality [that is, participate by representation in higher degrees of being or perfection], than those that represent only modes or accidents;"
          Descartes / Vetch, Pg 239 -- Meditation III

The next step in his argument is the critical one.   It is his premise that "Now, it is manifest by the natural light that there must at least be as much reality in the efficient and total cause as in its effect;"[Vetch, Pg 239] and "it is not less repugnant that the more perfect should be an effect of, and dependence on the less perfect"[Cottingham pg 172].   Having classified the three categories of ideas according to his notion of "perfection", he concludes that the cause (the formal reality) of some level of perfection must be equal to or greater in perfection than the idea that is the effect (the objective reality).   All of this he maintains is based on "logically necessary truths" -- or intuitions of the light of reason -- beyond challenge from the deceiving god/demon.

"When we apprehend that it is impossible a thing can arise from nothing, this proposition (ex nihilo nihil fit), is not considered as something existing, or as the mode of a thing, but as an eternal truth having its seat in our mind, and is called a common notion or axiom."
          Descartes / Vetch, Pg 319 -- Principles

"For it is not only manifest by the natural light that nothing cannot be the cause of anything whatever, and that the more perfect cannot arise from the less perfect, so as to be thereby produced as by its efficient and total cause, but also that it is impossible we can have the idea or representation of anything whatever, unless there be somewhere, either in us or out of us, an original which comprises, in reality, all the perfections that are thus represented to us;"
          Descartes / Vetch, Pg 308 - Principles

". . . for it is in the highest degree evident by the natural light, that that which knows something more perfect than itself, is not the source of its own being, since it would thus have given to itself all the perfections which it knows;"
          Descartes / Vetch, Pg 309 - Principles

Having thus set the necessary groundwork, Descartes finally embarks on his "Proof"of the existence of God.   He starts with the premise that he has an idea of absolute perfection -- an idea of God.   This idea, being an idea of his mind, has an objective reality.   But, he asks, what is the cause of this idea?   By his definition of objective and formal reality, he can conclude that whatever the cause, it must have at least as much formal reality as it does objective reality.   Since his idea is that of absolute perfection, then the cause of the idea must also possess absolute perfection.   Therefore, this idea cannot have an adventitious cause, since it has already been demonstrated through his method of doubt that the senses are flawed and hence imperfect.   Nor can this idea have a factitious cause (be made by himself), since it has already been demonstrated that he can be fooled by his evil god/demon, so that he, himself, must be considered flawed and imperfect.   Therefore, his idea of God must be innate.   But if it is an innate idea, what has caused the creation of such a perfect innate idea.   The innate idea of absolute perfection must be the effect of a cause that has at least as much formal reality.   Descartes reasons that the only way that he could come by this innate idea of his of an absolute perfection, is if something of equal or greater perfection caused the idea in him.   Therefore God must exist.

Descartes follows this proof with a second line of reasoning.   He uses the same approach, from the same premises, to reason from the indubitable fact that he ("I") exists to the inescapable conclusion that only a omniperfect God could have created a thing such as "I"that contains an idea of such perfection.

None of the premises of Descartes reasoning is based solely on his "clear and distinct ideas".   Each premise in his reasoning, Descartes states is true "from the natural light".   In other words, Descartes very clearly maintains that the premises to his proof of the existence of God are immune to the deceptions of any deceiving god/demon, and are therefore to be considered as certain.  

"And, truly, I see nothing in all that I have now said which it is not easy for any one, who shall carefully consider it, to discern by the natural light;"
          Descartes / Vetch, Pg 245 -- Meditation III

"In truth, it is perfectly clear and evident to all who will attentively consider the nature of duration, that the conservation of a substance, in each moment of its duration, requires the same power and act that would be necessary to create it, supposing it were not yet in existence; so that it is manifestly a dictate of the natural light that conservation and creation differ merely in respect of our mode of thinking [and not in reality]."
          Descartes / Vetch, Pg 246 -- Meditation III

Once he has proven that his omni-benevolent God exists on the basis of this degree of certainty, he can then argue that this God could not possibly be a deceiver.   And that conclusion allows him the further consequence that all of his "clear and distinct perceptions"can be regarded as true.   So Descartes cannot be accused of reasoning in a circle when he argues that everything we clearly and distinctly perceive is true because God exists and is not a deceiver


[AT] Adam, C. & Tannery, P. (eds.)   Oeuvres de Descartes, revised ed., 12 vols. Paris.   1964-1976.   [as quoted in various sources]

Cottingham, John & Stoothoff, Robert (translators);   Descartes, Selected Philosophical Writings, Cambridge University Press, Cambridge, England. 1988. ISBN 0-521-35812-4.

Dennett, Daniel C.;   Descartes'Argument from Design.   Tufts University.   2006.   Downloaded August 15, 2008.   URL=<>

Markie, Peter.   "The Cogito and its Importance", in The Cambridge Companion to Descartes, John Cottingham, ed., Cambridge University Press, Cambridge, England. 1992. ISBN 0-521-36696-8.

Rose, L.E.   "The Cartesian Circle"in Philosophy and Phenomenological Research, Vol 26, No. 1. Sept. 1965. Pgs 80-90.   URL=<>

Williams, Bernard;   Descartes: The Project of Pure Enquiry, Penguin Books, New York, New York. 1990. ISBN 0-14-013840-4

Vetch, John (translator);   Descartes: The Method, Meditations, and Philosophy, Universal Classics Library, Walter Dunne Publisher, London, England, 1901. downloaded from The Online Library of Liberty, August 8, 2008. URL=<>

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