Third meditation

The existence of God


  1. Recap of what I’m sure of up to now:I am a thinking thing, I can be certain of what exists at least within me.
  2. Lay down a general rule:whatever I perceive veryclearlyanddistinctlyis true
  3. The distinctness of my ideas does not come from perceptions
  4. Removing thedeceiving godquestion
  5. First demonstration of God’s existence
    1. Pinpoint different classes of ideas
    2. I have perceptions regardless of my intention to have them
    3. From the ideas of finite substances to the idea of God as an infinite substance
    4. The axiom onthe principle of causation
    5. From ideas to reality
    6. God as the only idea I can’t be the cause of
  6. Second demonstration of God’s existence
    1. From whom should I derive my existence
    2. creation and conservation
    3. the only being which preserves and causes himself
  7. How do I receive the idea of God
  8. God is not a deceiver

18thNovember 2020

The first point Descartes makes is a general rule regarding knowledge:

So now I seem to be able to lay it down as a general rule that whatever I perceive very clearly and distinctly is true

Clearness and distinctness are the key to perceiving what’s actually true.
While looking at geometrical truths, I can’t be fooled that they’re not so.

A critic: since Descartes bases his demonstration of God on ideas, either the demonstration doesn’t work because it’s built on unstable elements, or it’s useless because we already know our ideas are certain.

Descartes’ reply:
We have to distinguish the present evidence and what God warrants. We need God to preserve the authenticity that our past evidence is true.

I can doubt of this kind of truth only if it appears as a class of ideas.

Two substances:

  • thinking substances
  • corporeal substances: extension

(Single bodies are a modification in extension and accidents of a unique corporeal substances)

Twoa posterioridemonstrations of God (starting from a property of the mind up to the definition of God):

  1. From the idea of God to the existence of God
  2. From the existence of the “I” who has the idea of God to the existence of God.

In both cases we’re starting from something we know. We couldn’t start from the world and have a cosmological approach, at this point Descartes didn’t prove the actuality and accuracy of perceptions.

First demonstration of the existence of God

Three kinds, classes of ideas:

the idea of God is innate, as innate are ideas about the world’s of physics without having lived in the world

  1. innate ideas
    geometry, etc.
  2. adventitious ideas
    related tojudgment: they come from the external world
  3. invented(innate, fictitious, factitious)ideas
    the result of a thought process within me

Principles of causation

An axiom about the cause and effect relation:

Concerning every existing thing, it is possible to ask what is the cause of its existence. The question may even be asked concerning God

Second set of replies to theMeditations

It can never be denied thateverything has a cause, ideas included.

Something can’t have more degrees of reality than its cause, therefore,an infinite being can't be yielded by a finite being.

Entities which are real and exist cannot be generated by something which doesn’t exist.

Lexical note

In Descartes’ lexicon:

  • Objective reality: the reality of an entity in my thoughts.
  • Formal realityoractual reality: the reality of things which exist in the real world.

The only way to move from my ideas to formal reality is to findthe idea of a being I can't create. Of course, I can’t have enough reality as the idea of God.

The premise that my knowledge is infinity precedes what is finite is fundamental.

Descartes’ is the first “christian” philosopher after D’Aquino which stated that we’re able to positively know infinity, we’re able to conceive and imagine an infinite being which is infinite. Locke: my idea of an infinite being derives exactly from my limitations as a finite being.

God is an infinite substance while I’m a finite substance. The cause has to have at least as much reality as the effect, therefore, as finite I don’t have enough reality to produce the idea of God.

Since God is an infinite substance, only an infinite substance can be his cause; therefore, God is the cause of himself.

The extension of God

According to Descartes, God has no extension, but when Spinoza theorized a God both figuratively and actually extended, Descarteses’ vision collapsed to a merely non-extended God.

23rdNovember 2020

Why can’t I be cause of the idea of God?

In a certain sense, the definition of God is prior to the definition of myself. Anticipation of Hegel: infinity is the ground concept, the base of any discussion.

Second demonstration of the existence of God

If I were the cause of myself, I’d have no needs, no desire, no aspirations, since I could achieve anything by simply wanting and being the cause of it. I’d also have the power to create my accidents

We have a finite, partial understanding of God, nevertheless a true understanding of him.

It’s fundamental the understanding that the I possesses an idea of God

What if the self was eternal, then no cause?

To create and to preserve something is the same action: thetheory of eternal creation. Even if we were eternal, we couldn’t live without an entity to preserve our existence.

We don’t need to find a cause for the beginning of time, but for every moment of the existence of a being, since it’s preserved by God and its lasting and survival across time isn’t given, but granted by its cause.

There isn’t a problem, as in D’Aquino, in conceiving infinite regression, since it’s not needed a “beginning” to demonstrate God’s existence and causality.

The source of the idea of God

The source of the idea of God is strongly related to the nature of innate ideas, treated in theFifth Meditation. God left in me a mark of his creation, the craftman’s mark, by leaving the idea of him.

Since God created me, and I am born with the idea of God, it is impossible to be as I am without God existing.

The idea of God can’t be adventitious.

The main properties of an innate idea are precisely that we can’t add or remove anything to / from this innate ideas


God is not a deceiver, I have no reason at all to doubt he’s deceiving me.

To be a deceiver means to miss something, to be not complete, not perfect; of course this would clash with the perfect nature of God

Fourth Meditation



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