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The Hungry Hundred Book Club Message Board › Decartes’ Third & Fourth Meditations summaries/notes

Decartes’ Third & Fourth Meditations summaries/notes

user 45680652
Singapore, SG
Post #: 5
There was a 'Philosophy 100' meet-up to discuss Descartes’ Third and Fourth Meditations yesterday, and it was suggested that these notes be posted up here. These were written based on my interpretation of the text (which is of course not the only possible one). While Descartes was a very organised and systematic thinker, I think he was not quite as organised a writer. Here I’ve tried to convey the main flow of his arguments, and succinctly stitch together the main points, without getting too sidetracked into definitional discussions or bogged down in tedious technical terms. More technical accounts can be found elsewhere online such as on SparksNotes.

Introduction to Third and Fourth Meditations

Descartes has so far established that he exists as a thinking (i.e. conscious) thing, but he has not yet established that any of the things in his mind correspond to actual things in the world outside his mind.

He will now go through the ideas he is thinking, and look for an idea that proves the existence of something outside his mind. The ideas in his thinking are like raw material, from which he wants to draw out firm knowledge of the external world.

But he can’t just take any idea in his mind – he must be sure it is a clear and distinct idea. If it’s not clear and distinct, but just a hazy and muddled idea, then he cannot even be sure the idea is what he thinks it is. It would be like some faulty piece of raw material.

It’s like if you’re a boss looking to employ someone, you can’t just try out any person who comes along; they must give you a clear and distinct profile or qualifications. They can’t just give you a hazy and muddled ramble about how awesome they are, otherwise you don’t even have a clear and distinct conception of who they are and what they can do.

An example of a clear and distinct idea in Descartes’ mind is his idea that as a thinking thing he exists. Another clear and distinct idea in his mind is his idea of arithmetic (2+3=5), although he doesn’t yet know if that clear idea corresponds to a truth beyond his mind, because it is still conceivable that a supremely powerful being might be deceiving him through such ideas.

The key piece of ‘raw material’ he will focus on now is the idea of God; by examining this idea he feels that he can prove there truly exists something outside his mind, and it will also show that this something is a supremely powerful being who is not deceptive. (He’ll be killing two birds with one stone.)


The Third Meditation contains what has come to be known as Descartes’ “Cosmological Argument” for God’s existence. He will offer not one but two lines of argument: firstly, God must exist to cause the idea of himself to exist in my thoughts; secondly, God must exist to maintain my continuous existence.


1. In the previous Meditation, I discovered that as a thinking thing I exist.

2. If I exist, then something must have caused me and my thoughts to exist.

3. This cause must have at least the same amount of reality as me and my thoughts.

4. When I hold an object as an idea in my thought, the cause of this idea cannot have less reality than that object I’m thinking of. (An analogy is a beautiful scenery inspiring a painting: the actual scenery cannot have less reality than the scenery painted on the canvas. Or when a life inspires a memoir: the actual life cannot have less reality than the life depicted within the memoir.)

5. Now when I go through all the ideas I have in my thinking, pretty much all of these ideas could conceivably have been caused by me. My ideas of ‘physical entities’ could all have been created as mere mental concoctions by me. My ideas of ‘external sensory perception’ could be my mind’s own murky, muddled self-confusions.

6. But there is one idea in my thoughts that I could not be the cause of: the idea of God. Here’s why not:

7. This idea I have of God is the idea of an infinite, perfect, independent substance by virtue of which all other things exist.

8. (And this is not just some muddled self-confusion, because I conceive of this idea very clearly and distinctly – just as I conceive of my existence as a thinking thing clearly and distinctly.)

9. Now an infinite substance would have more reality than a mere finite being. Therefore, the idea of an infinite substance couldn’t have been created by a mere finite being, nor could it have been concocted from the idea of finitude and finite things.

10. I myself am a mere finite being, and so I could not have created this idea of an infinite, perfect substance.

11. Hence, this idea must have originated not from me, but only from a substance that exists beyond my mind and that matches the attributes of infinity, perfection and independence.

12. In other words, this substance, i.e. God, must truly exist, to have implanted this idea of himself in my thoughts.
13. Now in addition, I want to also argue that my own existence (as a thinking thing) can be continuously maintained in time only by such a being as God.

14. The only other possible suggestions are that I continuously maintain myself in time; or that I am continuously maintained by a being less perfect than God; or that my parents continuously maintain me. These are not credible alternatives, for the following reasons.

15. If I were maintaining myself in time, then since time is infinitely divisible into moments, each arising from the last, at each moment I would have to be creating myself for the next moment; I am not aware of having any such ability to continually create myself (as a thinking thing) for each next moment. So I can’t be the one maintaining my existence.

16. If my existence is maintained by some other being who likewise had the idea of God but who is less perfect than God, then what maintains that being’s existence? Suppose it is maintained by yet another imperfect being; what then maintains that being’s existence? The inquiry can arise again, and again, until eventually I would arrive at the first cause that is God, who as a perfect, independent being would be self-sustaining.

17. And as for my parents, even if it were to be true that I derived my birth from them, that bodily origination doesn’t mean they’re continuously maintaining my existence as a thinking thing.

18. So the only option left is that it is God who continuously maintains my existence in time as a thinking thing. Therefore God exists.
19. So just by rigourous reason and introspective thought, without relying on external sensory material, I’ve discovered two lines of argument proving God exists. And since God is perfect, and deceitfulness is an imperfection, he would not deceive me (as I had previously hypothesised an evil genius demon as doing). So I need not have the sort of mesmeric doubt that I did in the previous Meditations, and can take it easy a bit.

Descartes’ next problem is, given that there exists this God, who is so awesome and non-deceitful, why and under what conditions will I nevertheless have some false beliefs and erroneous judgements? Hence the next Meditation’s title: Of the True and the False.
user 45680652
Singapore, SG
Post #: 6
(continued from above)

Even if we’re not convinced by Decartes’ arguments about God, they’re still fascinating because they bring to mind crucial philosophical questions:

1. Is knowledge founded on the senses, or on abstract reasoning?

For the rationalists (Descartes, Spinoza, Leibniz), abstract reasoning could be used to acquire knowledge of reality far beyond the senses (such as the nature of God and the universe).
They were particularly inspired by mathematics, in which you can discover proofs without any reference to the sensory world, just by doing abstract mathematical reasoning.
Descartes and Leibniz are regarded not only as great philosophers, but also as two of the most important pioneers in the history of mathematics. (Leibniz is credited as the co-inventor of calculus, along with Newton.)

But for the British empiricists (Locke, bishop Berkley, Hume), knowledge has its roots in the senses.
The further away you drift from the sensory perception, the less credible your ideas.

2. Should a person relate to the prospect of God through reason, or through a leap into faith?

For Descartes, God is something to be known with certainty through the great power of reason.

But for the Christian existential philosopher Kierkegaard, all the power of reason cannot fully validate religion. Engaging with God involves a leap to faith, with no certainty that what you are doing and believing in is necessarily correct or valid.


In the Fourth Meditation, arguably the most theological of the six meditations, Descartes develops an epistemology that would cohere with his newly-meditated ideas about God.

My summary:

1. If God is perfect and thus non-deceitful, why does he let me have false beliefs and erroneous judgements? Why would a perfect God give me a mental faculty that leads me into error? There are several solutions to this.

2. Firstly, perhaps I should look at it as a glass half-full, rather than a glass half-empty. God doesn’t damn me with a faculty that deceives me; rather, he gifts me with a faculty that lets me discern truth, just not a perfect one.

3. But why doesn’t he give me a perfect one? If God is a perfect being, then his creations should be perfect, including me. So isn’t it the case that I ought to have been given a perfect faculty for discerning truth?

4. Well, secondly, perhaps God has good reasons for not giving me this perfect faculty - it’s just that I as a mere finite being have insufficient capability to comprehend his reasons and infinite wisdom.

5. Thirdly, perhaps all God’s creations are perfect, not when viewed as individual parts, but only when viewed together or in relation to one another. So I shouldn’t expect myself to be perfect when viewed merely as an individual creation removed from the context of the greater whole.

6. Fourthly, God being perfect means he possesses the ability to make his works perfect, but it doesn’t mean he’s obliged to use this ability for every single one of his works. So just because some of God’s works are imperfect, that need not be seen as going against God’s nature as a perfect being.

7. Fifthly, perhaps error arises from my free will. Let’s elaborate on this. When I examine my mind, I find God has given me the faculty of knowing (i.e. understanding) and the faculty of choice (i.e. free will).

8. I find that my understanding is imperfect: there are many things I don’t understand. (As established in the reasons above, this imperfection does not necessarily contradict God’s nature as a perfect being.)

9. In contrast, I find that my free will is perfect. It is perfect, not in the sense of having limitless options to choose from, but rather in the sense that when I am presented with the possibilities of doing something or not doing it, my picking one possibility over the other is not determined by an external force. I have the ability to pick one possibility over another, on the basis of my understanding that possibility to be true and good.

10. Now to find out why I commit error, I cannot just examine my faculty of knowing alone, or just my faculty of choice alone; I must view these two faculties in relation to each other:

11. Error arises when I exercise my perfect free will beyond the limitations of my imperfect understanding. When I do not conceive an idea clearly and distinctly in my understanding, and yet I still use my free will to judge that idea to be true or false, then I commit error (and sin), for I choose to pass judgement where I really should choose to suspend judgement.

12. Thus error does not come from the imperfect understanding God gives me, nor does it come from the perfect free will he gives me, but rather it is the result of my not using these two God-gifted faculties in proper tandem with each other.

13. But isn’t it imperfect of God to give me such perfect free will, and thus to make me capable of exercising it beyond understanding? Shouldn’t he have reduced my free will such that it can’t be exercised beyond understanding’s limits?

14. No, because the free will is not divisible into degrees, and so it can’t be reduced by degrees, it is something that either I have, or I don’t. For God to ‘reduce’ my free will, he would have to determine my actions, and destroy my free will altogether. (Freedom of will here is understood not as extension of the number of options available, but rather as autonomy in the act of choosing.)

15. Furthermore, I should feel thankful for a perfect free will, because my other faculties in their imperfection make me dissimilar to God, and so it is mainly this perfect free will that allows me some similarity to perfect God.

16. In conclusion, I ought to ensure I have clear and distinct understanding of an idea before I choose to judge it to be true. If I lack clear and distinct understanding of an idea, I must hold back from judging it to be true. By this criterion, my entry into error is thus something I am responsible for, it is not the responsibility of some external power.

Previously, Descartes was groping around in the murkiness inside and outside his mind, searching for donkeys on which to pin the tail of certainty.

But here he really starts to show he is not just an inventor of useful hypotheses, not just someone who analyses and deduces concepts, but also a system-builder, a synthesiser of concepts (despite the flaws of his edifice).

He goes from carving out particular concepts like the Cogito (i.e. the thinking existing self) and God, to constructing a model of the mind that would synthesise a metaphysics of God with an advocacy of rational inquiry and critique. For Descartes the mind is indebted to God, yet knowledge is founded not on any religious text or received wisdom or external force, but rather on a thinker’s own understanding and autonomous, sound judgement.

So even in this rather maligned Meditation, the burgeoning spirit of intellectual modernity seems very much present.
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