Descartes' second argument for demonstrating the value of God rests on the axiological position that being equates to value (or perfection), and that the more degrees of objective reality a thing possesses, the greater its value or perfection.
Substances are thus superior in value to accidents: Undoubtedly, the ideas that represent substances amount to something more—they contain within themselves more representative reality—than do the ideas that merely represent modes [or accidents] ¹.

This identification of being with value leads to God being the supreme value—sovereign perfection—because He possesses the most objective reality, for two reasons.

First, because He is infinite: His being has no limitations or negations; He is entirely being: God, on the other hand, I take to be actually infinite, so that nothing can be added to his perfection ².
Second, because He gives Himself existence: It is a common notion that if a thinking being doesn't depend on anything else, then it is God. Why? Because if something's existence is due to itself, we can't doubt that it will have given itself as many perfections as it could recognize ³.

The corollary of this equation—being equals value—is that nothingness has no value: I also have what you might call a negative idea of nothingness (that which is furthest from all perfection) ⁴.

This axiological position, however—the claim that being has value and nothingness has none—cannot be accepted as self-evident; this is precisely what nihilism contests. It is also contested by the dreamer, who holds that what does not exist—what is dreamt or imagined—has more value than what merely exists in reality.
The persistence of this unfounded doctrine suggests that while Descartes subjected his epistemological certainties to radical doubt, he did not apply the same scrutiny to his axiological ones.
Once again, then, Descartes' second argument for the value of God is seen to lack a solid and certain foundation.

Descartes' third argument for proving that God is the supreme value is based on the axiological position that the cause inherently possesses more value (or perfection) than the effect: One should note that we have ascribed to God the dignity inherent in being a cause in such wise that no indignity inherent in being an effect would follow thence in him […] Although I have granted that God can in a certain sense be called the cause of himself, nevertheless nowhere have I in the same way called him an effect of himself ⁵.

We have already encountered this axiological position in our study of Nietzsche ⁶, and we noted that this idea of aristocratic origin is entirely debatable: what issues from a humble or despicable source can infinitely surpass its origin in value; the effect, equally, can exceed the cause. We drew on examples such as Napoleon, who came from a modest Corsican family, or a river, which vastly exceeds its initial source in magnitude.
We might define axiological materialism as the doctrine that posits the inferior—chemical particles, biological cells—as the cause of the superior—consciousness, the mind—such that the effect is always greater than the cause.

Even if Descartes' second axiological position could be sustained, then, its opposite might equally hold, rendering it unfounded and far from indubitable—it is, in fact, doubtful. It cannot therefore be accepted as an absolutely certain truth, as Descartes appears to do. Like the first axiological position examined above, this one too seems to have escaped radical doubt; and in fact, neither of these two fundamental dogmas was subjected to it.

To summarise: the choice of terminology (using 'perfection' to denote value) and these three axiological positions together constitute what might be called Descartes' implicit doctrine of values.

Each of these points has been shown to be problematic; Descartes' axiological doctrine, while not necessarily false, is at the very least questionable. As such, it ought to be subject to the epoché—to the suspension of judgement and radical doubt—through which Descartes searches for something truly indubitable. Yet this is not the case. The doctrine of values is neither stated nor deployed in the first two Meditations, where Descartes affirms and then progressively rejects ideas that prove doubtful. It surfaces only from the third Meditation onward—after the Cogito—where Descartes claims to have grasped an indubitable truth: I am, I exist—that is certain. But for how long? For as long as I am thinking ⁷.

The difficulty of moving from this initial truth to a second one is plain. How is Descartes to move beyond the ego—whose existence he has established—to the truth of the world? As we know, he must rely on the truth of an 'intermediary': God. His unwavering requirement to accept only unquestionable truths, and to introduce nothing doubtful into his reasoning, clearly remains in force. His progression must therefore be grounded in indubitable truths.

My contention is that it was at precisely this moment—when Descartes sought to bridge the gap between the ego and the world through the mediation of God—that he brought into play this dubious axiological doctrine, despite the fact that only unquestionable judgements were supposed to be admissible.

1. Metaphysical Meditations, III
2. ibid.
3. Letter to Mersenne, 15 November 1638
4. Metaphysical Meditations, IV
5. Answers to fourth objections
6. Book I
7. Metaphysical Meditations, II