Rene Descartes · Philosophy
To trust his own reason and reach the world beyond his mind, Descartes argues he must first prove that a perfect, non-deceiving God exists - guaranteeing that whatever he perceives clearly and distinctly is true.
Descartes has won one certainty - the cogito - and from it a rule: whatever he perceives clearly and distinctly is true. But a shadow remains over the rule itself. As long as it is even possible that an all-powerful deceiver made his mind so that he errs even when he perceives things most clearly, the rule cannot be fully trusted. While he is actually attending to a clear and distinct truth (like the cogito, or that 2 + 3 = 5), he cannot doubt it. But the moment his attention shifts, the old worry creeps back: how do I know my mind is not so flawed that even its clearest perceptions are false? This is sometimes called the ‘problem of the Cartesian circle’s shadow’, but its role in the argument is plain: to escape the demon for good and trust reason in general, Descartes needs a guarantee that his clear and distinct faculties are reliable. And the only thing that could underwrite such a guarantee, he concludes, is the existence of a perfect, non-deceiving God. So the next task - strange as it sounds for a philosophy that began with the self - is to prove that God exists.
Descartes’ first proof of God (in the Third Meditation) is a ‘causal’ argument that starts from inside his own mind. Among all his ideas, he finds one of a supremely perfect being: an infinite, eternal, omniscient, omnipotent God. Now, he reasons, every idea must have a cause, and there must be at least as much ‘reality’ in the cause as in the effect - something cannot come from nothing, and the greater cannot come from the less. But Descartes himself is a finite, imperfect, doubting being. How could a finite, imperfect mind produce the idea of an infinite, perfect being? He could not have invented it from his own limited resources, any more than a small candle could produce the heat of the sun. The idea of infinite perfection has more ‘reality’ in it than its finite, imperfect possessor. Therefore, Descartes concludes, the idea must have been placed in him by a being that actually has all that perfection - that is, by God himself. The very presence in my mind of the idea of a perfect God proves that such a God exists, as its cause.
With God proved to exist, Descartes can finally climb back out of the pit of doubt and recover the world. The chain runs like this. God exists and is supremely perfect. A perfect being cannot be a deceiver, for deception springs from malice or weakness, which are defects, and a perfect being has no defects. Therefore God is no deceiver. Therefore the faculties God gave me - including my reason, and my clear and distinct perception - are not systematically misleading when I use them properly. So whatever I perceive clearly and distinctly is true, and I can trust it generally, not just while I stare at it. This finally lifts the shadow of the evil demon: the demon hypothesis is ruled out, because the mind’s maker is good. From this secured trust in reason, Descartes can then argue that the external world exists (since I have a strong natural inclination to believe my sensations come from external bodies, and a non-deceiving God would not give me so strong an inclination if it were entirely false), though the world may not be exactly as the senses paint it. The doubt is answered, reason is vindicated, and knowledge can be rebuilt - all resting, ultimately, on the proof of a good God.
This is the opening of the lesson. The rest — the dialogue, the primary source, and the recall — is in the app.
You learned that Descartes proves God exists in order to guarantee that clear and distinct perceptions are true - escaping the worry that an evil demon makes him err even when he is most certain. Explain how God secures the trustworthiness of reason for Descartes.
Leads to Anselm.
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