Fifth meditation

The essence of material things, and the existence of God considered a second time


  1. The nature of innate ideas
  2. analysis of mathematical truths
  3. innatism of mathematics
  4. the properties of innate ideas
  5. third demonstration of God’s existence
    1. Essence and existence are entangled
    2. Consideration of the logical objection
    3. God’s existence is intrinsic in its perfection as a mathematical property is intrinsic in the existence of a figure

The subject of the whole meditation is innatism.

The content of innate ideas is true, immutable and independent from my other beliefs; I can’t add or remove any attributes to ideas which are innate, since they re not dependent on my mind.

For example, if we take a geometrical figure, we can achieve new knowledge through it, this doesn’t happen with factitious ideas.

Example of Hamlet: an idea which isn’t innate –his eyes– can’t be conceived if not told: innate ideas are naturally in the mind and can’t be modified, but properties can be added and built upon them.
Of course innate ideas are not derived from experience at all.

Furthermore, I can’t condition nor arbitrarily decide their content.

Geometry and mathematics in general, as Aristotle himself stated, doesn’t come from experience and, as innate ideas, they can’t derive from notions of figures I encountered in reality.

An echo to Plato’s theory of knowledge.

Third demonstration of God’s existence

Differently from the demonstrations explained in the Third Meditation, this demonstration is a priori: the idea of God is the cause of God himself. From the definition of God, we can derive God’s existence.

This demonstration of God has not an end in itself, but it’s a reinforcement of the thesis on the matter about entanglement and relations between essence and existence

A demonstration modeled on mathematical demonstration.

Descartes was well aware of the critics to Anselm’s Ontological Demonstration, in this demonstration he intends to prove that in this way an ontological demonstration is indeed possible. He’s implicitly confronting his predecessors’ critics.

classes of innate ideas:

  1. God
  2. body
  3. mind

After D’Aquino it was natural to distinguish between existence and essence.

It’s a contradiction to deny God’s existence as it is so to deny a geometrical property: God’s existence is intrinsic in his perfection.

A complete change of perspective from D’Aquino, it’s a matter of essence.

Descartes turns the critic of D’Aquino to Anselm against D’Aquino himself: existence inseparable from God. This doesn't depend on one's thinking, but it's intrinsic in the definition of God.

The content of the idea of God it’s different from the content of all other ideas: we aren’t moving form the mental domain to reality, we already are within reality.

Note: the idea of God is the same for everyone



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