Descartes gives three arguments for the existence of God  in his Meditations on First Philosophy.  This entry discusses the first argument and commenter Elliot's objection to it. We can call it the argument from the representational content of the God-idea.  In a subsequent entry I hope to set forth the argument in full dress and point out its weaknesses. For now I offer a quick sketch of it as I interpret it. After the sketch, Elliot's objection, and finally Descartes' anticipation of the objection.  It will lead us into some deep waters. So put on your thinking caps and diving gear.

Sketch

The argument attempts to move from the idea of God, an idea that we find in ourselves, to God as the only possible cause of the idea. It is not the mere occurrence of the idea in us, the mere fact of our having it, that is the starting point of the argument, but what I will call the representational content of this idea. Ideas are representations. They occur in consciousness as representings, acts of representation, but they purport to refer beyond themselves to realities external to consciousness.  Which ones? The ones indicated by their representational contents. A three-fold distinction is on the table: mental act, representational content  of  the act, extramental thing presented to consciousness under the aspect of the content.  Cogitatio, cogitatum qua cogitatum, res extramentem. (An anticipation of Husserl's noesis-noema schema?)

In the jargon that Descartes borrows from the scholastics, the representational content of an idea is its realitas objectiva. By 'objective reality,' Descartes does not mean something mind-independent; he means the representational content of the act of representing which, while distinguishable from the act, is inseparable from it.  Every act has its content, and every content is the content of an act. By 'formal reality,' he means items that exist in themselves and thus independently of us and our representations. The direction of the first argument is thus from the realitas objectiva of the idea of God to the realitas formalis of God.

Descartes takes it for granted that there are degrees of reality, and therefore degrees of objective reality. Thus an idea that represents a substance has a higher degree of objective reality than one that represents an accident. The idea of God, Descartes writes, "certainly contains in itself more objective reality than do those by which finite substances are represented." (Adam-Tannery Latin ed., p. 32) 

Now according to Descartes, the lumen naturale (natural light) teaches that "there must be at least as much reality in the total efficient cause as in its effect, for whence can the effect derive its reality if not from the cause?" (Ibid.) The more perfect cannot be caused by or be dependent upon the less perfect. The more perfect is that which contains more objective reality. This holds not only for external things existing in formal reality, but also for  ideas when one considers only their objective reality. And so the realitas objectiva of the God-idea can only have God himself as its cause. Ergo, God exists!

I will note en passant, and with a tip of the hat to Etienne Gilson, just how medieval this reasoning by the father of modern philosophy is! It is very similar to the reasoning found in the Fourth Way of Aquinas. Descartes takes on board the degrees-of-reality notion as well as the idea of efficient causality together with the related notion that the efficient cause must be at least as real as its effect. These are stumbling blocks for post-Cartesian thinkers, a fit topic for  subsequent posts. 

Elliot's Objection

I hold Descartes in high regard, but I have doubts about the claim that no human is sufficient to cause the idea ‘God.’ Suppose a human who is (a) aware of himself as a person, and thus has the idea ‘person,’ (b) aware of axiological relations such as ‘greater than,’ and (c) understands the concepts of infinity and supremeness. Why couldn’t such a human come up with the idea ‘God’ by reflecting on ‘human person,’ ‘greater than,’ 'supremeness,' and ‘infinity’? Why can't an Anselm come up with the idea of the greatest conceivable being? Why can't a Plato come up with the idea of a perfect being (Republic, Book II)?

Elliot's objection has a 'Feuerbachian' flavor. Ludwig Feuerbach held that God is an anthropomorphic projection.  What he meant was that there is no God in reality, there is only the idea of God in our minds, and that this idea is one we arrive at by considering ourselves and our attributes.  We take our attributes and 'max them out.' We are powerful, knowing, good, and present, but limitedly, not maximally. Although we are not  all-powerful, all-knowing, all-good or omnipresent, we can form these maximal predicates and imagine them true of one and the same being, which we then project into external reality. By this unconscious mechanism we fabricate the idea of God. But since the mechanism of fabrication is unconscious or perhaps subconscious we fool ourselves into thinking that there really is such a being as we imagine. The God idea, then, turns out on my reading of the Feuerbachian analysis to be factitious in  Descartes' tripartition. (He distinguishes between innate, acquired, and factitious (made up, from the L. facere, to make)  ideas. As examples of the last-mentioned, Descartes cites sirens and hippogriffs.)  In sum, the presence in us of the God-idea is adequately explained by our own  unconscious or subconscious doing. No God need apply.

Descartes' Anticipation of the Objection

Descartes seems to have anticipated the objection. He writes:

But possibly I am something more than I suppose myself to be. Perhaps all the perfections which I attribute to the nature of a God are somehow potentially in me, although they [(are not yet actualized and)] do not yet appear (47) and make themselves known by their actions. Experience shows, in fact, that my knowledge increases and improves little by little, and I see nothing to prevent its increasing thus, more and more, to infinity; nor (even) why, my knowledge having thus been augmented and perfected, I could not thereby acquire all the other perfections of divinity; nor finally, why my potentiality of acquiring these perfections, if it is true that I possess it, should not be sufficient to produce the ideas of them [and introduce them into my mind].

Nevertheless, [considering the matter more closely, I see that] this could not be the case. For, first, even if it were true that my knowledge was always achieving new degrees of perfection and that there were in my nature many potentialities which had not yet been actualized, nevertheless none of these qualities belong to or approach [in any way] my idea of divinity, in which nothing is merely potential [and everything is actual and real]. Is it not even a most certain [and infallible] proof of the imperfection of my knowledge that it can [grow little by little and] increase by degrees? Furthermore, even if my knowledge increased more and more, I am still unable to conceive how it could ever become actually infinite, since it would never arrive at such a high point of perfection that it would no longer be capable of acquiring some still greater increase. But I conceive God to be actually infinite in such a high degree that nothing could be added to the [supreme] perfection that he already possesses. And finally, I understand [very well] that the objective existence of an idea can never be produced by a being which [38] is merely potential and which, properly speaking, is nothing, but only by a formal or actual being.

And certainly there is nothing in all that I have just said which is not easily known by the light of nature to all those who will consider it carefully. But when I relax my attention some¬ what, my mind is obscured, as though blinded by the images of sensible objects, and does not easily recall the reason why my idea of a being more perfect than my own must necessarily have been imparted to me by a being which is actually more perfect.

Evaluation

I am actually powerful, but not actually all-powerful. And  likewise for the other attributes which, when 'maxed-out,' become divine attributes. Am I potentially all-powerful? No. Descartes is right about this. But if I am not potentially all-powerful, all-knowing, etc., then my fabricated ideas of omnipotence and omniscience, etc. lack the objective reality they would have to have to count as ideas of actual divine attributes.  That seems to be what Descartes is saying.  He seems to be assuming that the objective reality or representational content of an idea must derive from an actual source external to the idea. That source cannot be a human being since since no such being is potentially omnipotent, omniscient, etc. and so could not ever be actually omnipotent, omniscient, etc.

But none of this is very clear because the underlying notions are obscure: those of causation, degrees of reality, and realitas objectiva.