In the very first lines of the ‘Third Meditation’ Descartes expresses that by looking deep within himself he can assert that he is a ‘thinking thing.' He claims that although he is not sure about the existence of things outside himself but he is confident that the modes of thinking, e.g. imaginations and sensations, exist inside him. Then Descartes tries to find out whether there is any other knowledge he may possess. In this scrutiny, he lays down that everything is true if he can perceive it very clearly and distinctly. Descartes then questions his judgment whether it can be deceived by some God who might endow him with a nature that he could be deceived, even about what can be perceived very clearly and distinctly. Therefore, logically, Descartes should first examine if any God does exist. (Descartes 1984, 24-25)
To do so, Descartes divides up his thoughts into categories so he may figure out that truth and falsity pertain to which category. He names some of his thoughts that are images and conceptions of thing as ‘idea’, while the idea of God falls under this category. He asserts that he also has some thoughts like wills, fears, denials, or affirms that he calls them ‘affects’, and some other thoughts that are ‘judgments.' However, ideas and affects by themselves do not pertain to falsity. Descartes, then, introduces three sources for his ideas: either they are innate, or adventitious, or are made by his imagination. (Descartes 1984, 25-26)
However, he needs to investigate that whether any of the ideas he has does exist outside of him, and also to figure out if the ideas are alike external things. In response, through some inclinations and arguments, he expresses that the nature itself teaches him to think so. This presumption is the cornerstone of the ontological argument. It means the source of the idea of God could be outside of Descartes’ mind, and the idea might have been produced in his mind without his conscious assistance. (Descartes 1984, 27)
Descartes argues to show that he cannot be the source of the idea by appealing to the concept of ‘objective reality’. Ideas comparing to them vary in their objective reality, e.g. the idea of God which is infinite has more objective reality than the idea of finite things. Descartes, based on what he names it ‘natural light’ which cannot be doubtful, claims that there must be as much objective reality in the ‘effect’ as there is in the ‘cause’, and that ‘something’ cannot come from ‘nothing.' In other words, something which is more perfect cannot come from something which is less perfect. Then he applies this doctrine to ideas, precisely the idea of God. It means, by the same token, the idea of God with the utmost perfect attributes cannot be derived from Descartes’ mind itself as the latter is incomplete, and it cannot be borrowed merely from his thoughts without any impression from outside. (Descartes 1984, 27-30)
Descartes continues and expresses that he clearly realise that some of his ideas have such great objective reality that he can be certain that they are not derived from his thoughts. However, he is not the cause of this idea, therefore, necessarily there must be other thing in the world as the cause of this idea. Descartes then expresses that the idea of God, amongst other ideas (e.g. bodily things, angels, other human beings, God, etc.) is the only one that cannot be derived from his mind. The rest of the ideas might have been put together from some ideas Descartes has for himself, or, if not, he cannot be sure if they are true ideas, i.e. if they are the ideas of actual things. By ‘God’ Descartes mean a supremely intelligent, supremely powerful, independent, and infinite substance, by which he and whatever else exist, is created. However, based on what he has argued so far and by a self-scrutiny, it seems that none of these infinite attributes has been derived from Descartes himself as a finite substance. Therefore, God has to exist independently outside Descartes’ mind. (Descartes 1984, 27-30)
Then, to support his argument, he proposes some objections that may arise and tries to refute them accordingly. First, he argues that the idea of an infinite existence, here God, cannot be derived by negating the concept of ‘finite.’ He asserts that as the objective reality of ‘infinite’ is more than of the objective reality of ‘finite’ the perception of infinite has to have priority to the perception of finite. Second, he refutes that the idea of God is false, based on what he discussed previously in this meditation because it is the most distinct and definite idea he has. Third, he claims that his knowledge cannot grow gradually to reach the perfection of infinity, because, among others, his knowledge will never be in a stage of being incapable of further increase. In the rest of this meditation, Descartes provides some further hypothetical objections and refutes them. (Descartes 1984, 30-35)
Many objections have been raised to Descartes’ ontological argument such as Gaunilo’s ‘Perfect Island’ or Kant’s objection that ‘existence is not a predicate’, which although I do agree with the latter one and believe that is the strongest objection so far, but I will not address them any further to what already provided. However, here I like to object Descartes’ doctrine of ‘clear and distinct perception’ that he uses as a presumption and the cornerstone of his argument. It seems that for Descartes the perception of God, which is infinite with omni-attributes, is a brute fact. However, how it can be proved that the idea of God, like what Descartes describes, is clear and distinct for everyone? Descartes does not provide any logical ground for his ‘intuition’. Furthermore, in the same way, it can be objected that the idea of God is not a simple idea, but it consists of omni-attributes in which the concept of infinity is crucial. However, infinity cannot be perceived directly by itself and we can percept it in an incremental way: by denying any limitation to what we can perceive directly as finite. In other words, Descartes’ presumptions about perceptions and infinity are not ‘clear and distinct’ enough by themselves. Therefore, given that the Descartes’ presumptions are not self-evident, maybe his argument is absurd.
Descartes, René. 1984. "Third Meditation: The existence of God." In The Philosophical Writings of Descartes, 24-36. Cambridge: Cambridge University Press.