In the Fifth Meditation, Descartes argues that “from the fact that I cannot think of God except as existing, it follows that existence is inseparable from God, and hence that he really exists” (CSM 2:46). Caterus famously replied with the ‘existing lion’ objection (parallel to Gaunilo’s ‘Lost Island’): we can’t think of anything as an existing lion without thinking of it as existing, so the existing lion must exist (CSM 2:72). In fact, Caterus didn’t need to add ‘existing’ at all: existence is a necessary condition for the exemplification of any property whatsoever. Nothing can be red, blue, five feet long, intelligent, President of the United States, or anything else at all without existing.
One standard response to this objection is to switch to talking about necessary existence, which Descartes sometimes seems to do (CSM 2:83). At other places, Descartes talks about eternal existence (CSM 2:45). It is perfectly possible to be red or blue or five feet long (etc.) without having necessary or eternal existence, so this is a step in the right direction, but of course I can just as easily talk about a necessarily existing lion, and then we are off in the familiar direction of contemporary debates about modal ontological arguments.
I want to suggest, however, that Descartes has something altogether different, and much stranger in mind.
Descartes’s preferred formulation of his premise is that existence (or necessary or eternal existence) belongs to the nature or essence of God (CSM 2:45, 2:83). Descartes asserts that “apart from God, there is nothing else of which I am capable of thinking such that existence belongs to its essence” (CSM 2:47). This is, of course, a very odd claim to make given contemporary understandings of essences. If the essence of a thing consists in the set of properties it possesses in every world in which it exists, then existence belongs to everything’s essence. However, that this is not Descarte’s understanding of essences (I take it that for Descartes ‘essence’, ‘nature’, and ‘true and immutable nature’ are synonyms) is clear from Descartes’s discussion of the true and immutable nature of a triangle: “it is not necessary for me ever to imagine a triangle; but whenever I do wish to consider a rectilinear figure having just three angles, it is necessary that I attribute to it the properties which license the inference that its three angles equal no more than two right angles” (CSM 2:47, emphasis added). If, as the context suggests, this is supposed to be an elucidation of the true and immutable nature of a triangle, then it follows that, for Descartes, essences/natures are not closed under entailment. The nature of a triangle includes “the properties which license the inference that its three angles equal no more than two right angles,” but does not actually include the latter property itself.
This allows Descartes to affirm that other essences do not include existence. As he says in the ‘geometrical’ presentation of his arguments,
Existence is contained in the idea or concept of every single thing, since we cannot conceive of anything except as existing. Possible or contingent existence is contained in the concept of a limited thing, whereas necessary and perfect existence is contained in the concept of a supremely perfect being. (CSM 2:117, ax. X)
So it looks like a statement of the nature/concept/idea/essence of triangle would begin, ‘a possible rectilinear figure…’ whereas a statement of the nature of God would begin, ‘an actually existing being…’ As a result, the attributes of triangles we derive from the true and immutable nature are all being attributed to merely possible things, so no assertion of actuality is made, whereas in deriving the consequences of the nature of God an assertion of actuality is made. So when we do our a priori reasoning, starting from true and immutable natures and deriving their consequences, we get the actual existence of God.
Now Caterus is going to come back and say that the nature of his existing lion is to actually exist, and not merely to possibly exist. However, Descartes, unlike Anselm, denies that we are talking about definitions of words (CSM 2:82-83). The true and immutable natures, according to Descartes, are objective facts grasped by the pure intellect in clear and distinct perception. Descartes simply denies that he has any such grasp of a true and immutable nature of ‘existing lion’ (CSM 2:47).
To review, true and immutable natures are not mere definitions that can be stipulated, but objective facts to be grasped by the pure intellect in clear and distinct perception. These facts are not closed under entailment: they are the basic facts that we grasp first in our a priori reasoning. The other necessary truths must be deduced from them. The true and immutable natures are evidently something like definitions, but these are real, rather than nominal, definitions. God’s true and immutable nature defines him as a certain actually, necessarily, and eternally existing being, whereas the true and immutable natures of other things define them as merely possible entities. The true and immutable natures are supposed to be necessary truths, but since they are not closed under entailment we can’t just identify them with all of the necessary truths. So which ones are they and where do they come from? Descartes gives a surprising answer:
just as the poets suppose that the Fates were originally established by Jupiter, but that after they were established he bound himself to abide by them, so I do not think that the essences of things, and the mathematical truths we can know concerning them, are independent of God. Nevertheless, I do think that they are immutable and eternal, since the will and decree of God willed and decreed that they should be so. (CSM 2:261)
This is explained in more detail in an early (1630) series of letters to Mersenne. There, Descartes says that
The mathematical truths which you call eternal have been laid down by God and depend on him entirely no less than the rest of his creatures … God laid down these laws in nature just as a king lays down laws in his kingdom. They are all inborn in our minds just as a king would imprint his laws on the hearts of all his subjects if he had power enough to do so. (CSM-K 23)
Descartes’s view is that necessary truths, just like contingent truths, are divine decrees; it’s just that when God made his decrees, he decreed that some should be necessary/eternal and others should be contingent. Now it seems to me that the true and immutable natures are the basic decrees, the axioms of the system of eternal truths. So God didn’t directly decree that the interior angles of a triangle should sum to 180 degrees; he made some more basic decrees which entailed it, and these basic decrees form the true and immutable nature of triangle. The true and immutable nature of triangle is innate in us, but the other facts about triangles are not innate; they must be deduced from the true and immutable nature.
But now we run into a real oddity when we talk about the true and immutable nature of God. If true and immutable natures just are divine decrees does God just decree his own nature? Given Descartes’s radical voluntarism, I think the answer must be yes. Descartes says that, “the existence of God is the first and the most eternal of all possible truths and the one from which alone all others proceed” (CSM-K 24). The ‘all others,’ I think, include the truths about God’s nature. We can (only slightly misleadingly) think of this as if it happened in time: first, God existed, but had no nature. Then, he decreed the eternal truths, including his own true and immutable nature. Then, he created mankind in whom these truths are innate. In a sense, then, Descartes’s view is that God’s existence is necessary because God himself (who already existed before his existence was necessary!) decreed that it should be.
I have argued that Descartes’s ontological argument is, in certain respects, radically different from standard ontological arguments. So is it better or worse? Well, on the one hand, it’s not vulnerable to standard objections to ontological arguments. This is because it’s premise is not that nothing would count as God unless it existed (or existed necessarily/eternally). Rather his premise is that one of the eternal truths graspable by the pure intellect is that God is a certain actually existing necessary, eternal being. Do you find yourself having a hard time ‘grasping’ this truth? Meditate harder! On the other hand, if it comes down to this, Descartes’s argument turns out not to be much of an argument at all, and his non-argument relies on some crazy views in metaphysics, epistemology, and theology. On the whole, we’d do better to stick with Anselm.
(cross-posted at blog.kennypearce.net)