To what extent is Descartes’ intuition and deduction thesis successful? (25)

Introduction

• This is the constructive phase of Descartes’ Meditations

• He uses intuition and deduction to justify claims undermined by his methodological scepticism

• 1: Gaining a priori knowledge through intuition (the cogito)

• 2: Evaluation of the cogito

• 3: Deduction of the existence of a supremely perfect being

• 4: Evaluation of this

• 5: I deduce from God’s existence that there is an external world

• 6: Evaluation of this

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• The cogito is Descartes’ claim that he exists

• Descartes understands himself as a thinking thing of which he has a clear and distinct idea

• Even if an evil demon is deceiving him about physical objects, the evil demon cannot about his own existence

• If he doubts his existence, he must exist to be able to doubt it

• It is a true belief that cannot be doubted

• It is not known through experience

• It is a truth discovered by reason alone

• It is a clear and distinct idea because it is ‘open and present to the attending mind’ and is separated from other ideas

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• Descartes fails to establish the cogito

• All that is established is that there is a thought now, rather than an enduring self

• This is Hume’s objection; experiences provides no evidence of an enduring self

• So we have no reason to believe that there is one

• Descartes jumps to there being an enduring self, but this is not necessarily entailed in the cogito

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• From the cogito, Descartes attempts to gain a priori knowledge through deduction

• This involves drawing conclusions that necessarily follow the premises

• This is Descartes ontological arguments for God:

• P1: The idea of God is an idea of a supremely perfect being

• P2: A supremely perfect being has all perfections

• P3: Existence is a perfection

• C1: Therefore, God exists

• Descartes seems to treat this not as a deductive argument

• He treats it as self-evident intuition

• It starts with an innate concept of God that we may discover within our minds

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• Hume’s Fork responds to Descartes’ ontological argument

• Hume’s Fork states that there are two types of knowledge: Matters of Fact and Relations of Ideas

• Matters of Fact are synthetic a posteriori, whereas Relations of Ideas of analytic a priori

• Hume would argue that the ontological argument claims that something exists because of our a priori proof

• However, nothing necessarily exists, and no synthetic truths can be demonstrated a priori

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• Descartes’ final argument is that he can deduce that the external world exists from the existence of God

• P1: I exist

• P2: God exists

• P3: God loves me

• P4: Someone who loves me wouldn’t want me to be deceived

• P5: If someone who loves me is able to stop me from being deceived they would do so

• P6: God is all powerful

• P7: God therefore wants and is able to ensure my senses don’t deceive me

• C1: Therefore, my senses do not deceive me

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• Firstly, the argument for the external world relies on two other flawed arguments

• As well as this, the conclusions are severely limited

• They do not tell us anything about the nature of the world

• The cogito simply tells us that we exist

• It is thus limited to introspective knowledge

• The ontological argument simply tells us that if God exists then he exists

• It does not tell us that he actually exists