Lecture 6: Descartes

LECTURE 6: DESCARTES

LECTURE OUTLINE

In today’s lecture we will:

1.1.Become introduced to Rene DescartesBecome introduced to Rene Descartes

2.2.Begin our investigation into Descartes’ theory of realityBegin our investigation into Descartes’ theory of reality

3.3.Examine Descartes’ philosophical aims and methodExamine Descartes’ philosophical aims and method

4.4.Outline and critically consider Descartes’ arguments for:Outline and critically consider Descartes’ arguments for:

I.I. The existence of mental substancesThe existence of mental substances

II.II. The existence of GodThe existence of God

III.III. The existence of physical substancesThe existence of physical substances

5.5.Discuss the validity of Descartes argumentsDiscuss the validity of Descartes arguments

DESCARTES’ THEORY OF REALITY


Rene DescartesRene Descartes

Lived 1596 – 1650Lived 1596 – 1650

Another important figure in the history of Another important figure in the history of philosophyphilosophy

Discovered analytic geometryDiscovered analytic geometry

A pioneer of scientific discovery and the A pioneer of scientific discovery and the enlightenmentenlightenment

Possessed his own distinct philosophical methodPossessed his own distinct philosophical method

Endorsed a Endorsed a DualistDualist theory of reality (Substance theory of reality (Substance Dualism)Dualism)


Substance Dualism (a prelude)Substance Dualism (a prelude)

Descartes argues that reality is composed of Descartes argues that reality is composed of Two Two distinct distinct SubstancesSubstances::

1.1. Physical SubstancesPhysical Substances2.2. Mental SubstancesMental Substances

Physical Substances Mental Substances

Atoms Beliefs

Rocks Thoughts

Students Attitudes

Dogs Denying

Water Affirming

Chairs Thoughts about chairs


Why should we carve reality up into two substances?Why should we carve reality up into two substances?

Problem 1 (P1)Problem 1 (P1)

Our senses can (and often do) deceive usOur senses can (and often do) deceive us

So how can we trust any of our senses?So how can we trust any of our senses?

Which line is Which line is longest?longest?



Problem 2 (P2)Problem 2 (P2)

Traditional philosophy (before science) can only give us Traditional philosophy (before science) can only give us possiblepossible answersanswers

Nothing in philosophy is beyond dispute and nothing is certainNothing in philosophy is beyond dispute and nothing is certain

Q: Why does fire/heat always go upwards?Q: Why does fire/heat always go upwards?

Aristotle: Its essence is heavenly and when Aristotle: Its essence is heavenly and when released it tries to return back to its native released it tries to return back to its native essence.essence.



Overall problem: Overall problem:

Existing philosophical theories and our senses are unable to give us Existing philosophical theories and our senses are unable to give us Certain KnowledgeCertain Knowledge

Certain knowledge is to be preferred over uncertain knowledgeCertain knowledge is to be preferred over uncertain knowledge

Unless philosophy can arrive at certain knowledge its future is in Unless philosophy can arrive at certain knowledge its future is in doubtdoubt

Descartes’ aim:Descartes’ aim:

Descartes sought to build a new philosophy that:Descartes sought to build a new philosophy that:1.1. Arrived at certain knowledgeArrived at certain knowledge

2.2. Gave answers that were beyond disputeGave answers that were beyond dispute


The search for certaintyThe search for certainty

Mathematics do provide us with certain knowledge:Mathematics do provide us with certain knowledge:

1.1.Mathematical knowledge is not derived from the sensesMathematical knowledge is not derived from the senses2.2.Mathematical knowledge is beyond disputeMathematical knowledge is beyond dispute3.3.Its truth can be demonstratedIts truth can be demonstrated

2+2=4

Mathematical truths are discovered through Mathematical truths are discovered through Reason AloneReason Alone


The birth of modern philosophyThe birth of modern philosophy

Descartes attempted to apply the mathematical method (using Descartes attempted to apply the mathematical method (using reason alone) to philosophy reason alone) to philosophy

He attempted to use reason alone to find one thing which is He attempted to use reason alone to find one thing which is absolutely certain (beyond doubt, beyond dispute, not derived from absolutely certain (beyond doubt, beyond dispute, not derived from the senses)the senses)

The criterion of such knowledge is The criterion of such knowledge is Clarity Clarity and and DistinctnessDistinctness

Once found, Descartes hoped to use intuition and deduction to find Once found, Descartes hoped to use intuition and deduction to find further certainty.further certainty.

To find this one certainty Descartes tries proceeds by employing To find this one certainty Descartes tries proceeds by employing systematic (Cartesian) doubtsystematic (Cartesian) doubt


Cartesian DoubtCartesian Doubt

Descartes attempts to doubt everything that can be doubtedDescartes attempts to doubt everything that can be doubted

If there is any possibility of doubting something, it is insufficientIf there is any possibility of doubting something, it is insufficient

Descartes’ goal is to find a truth which is beyond doubt.Descartes’ goal is to find a truth which is beyond doubt.

On what grounds might we doubt the following:On what grounds might we doubt the following:

““This is my right hand, it has five fingers”This is my right hand, it has five fingers”

““The Earth revolves around the sun”The Earth revolves around the sun”

““I am teaching Phi-100 at DCCC”I am teaching Phi-100 at DCCC”

““I like the taste of ice cream”I like the taste of ice cream”

““The person teaching Phi-100 at DCCC exists”The person teaching Phi-100 at DCCC exists”

““The person teaching Phi-100 is human”The person teaching Phi-100 is human”

DESCARTES ARGUMENTS FOR SUBSTANCE DUALISM


I – The Existence of Mental SubstanceI – The Existence of Mental Substance

Descartes discovered that the one thing beyond all doubt is:Descartes discovered that the one thing beyond all doubt is:

““I think therefore I am” I think therefore I am” (Cogito Ergo Sum)(Cogito Ergo Sum)

1. It is certain that I exist1. It is certain that I exist

Even if I am being deceived about my own existence then there is still Even if I am being deceived about my own existence then there is still something (myself) being deceivedsomething (myself) being deceived

2. I am a mind or a thing that thinks2. I am a mind or a thing that thinks

To be able to doubt I must be thinkingTo be able to doubt I must be thinkingDoubting that I am thinking is contrary to reason and logic!Doubting that I am thinking is contrary to reason and logic!

Therefore: We can be certain that mind existsTherefore: We can be certain that mind exists

We can also be certain that We can also be certain that Mental Substance Mental Substance existsexists


II – The Existence of GodII – The Existence of God

Descartes uses his ‘First Principle’ to deduce two arguments for God’s Descartes uses his ‘First Principle’ to deduce two arguments for God’s existenceexistence

1. The Eidological argument1. The Eidological argument

Q: Where does the idea of perfection (or God) come from?Q: Where does the idea of perfection (or God) come from?

It cannot come from experience or the sensesIt cannot come from experience or the sensesCannot come from nowhereCannot come from nowhereI cannot merely invent the idea of perfectionI cannot merely invent the idea of perfection

Therefore:Therefore:

A1: The only rational answer is that the idea of perfection was placed A1: The only rational answer is that the idea of perfection was placed in our minds by Godin our minds by God

A2: God existsA2: God exists


II – The Existence of GodII – The Existence of God

Descartes uses his ‘First Principle’ to deduce two arguments for God’s Descartes uses his ‘First Principle’ to deduce two arguments for God’s existenceexistence

2. The Ontological argument2. The Ontological argument

A.A.God, by definition, is that being which is absolutely perfectGod, by definition, is that being which is absolutely perfect

B.B.It is more perfect to exist than not to existIt is more perfect to exist than not to exist

C.C.Therefore, to conceive of God it is necessarily to conceive of him as Therefore, to conceive of God it is necessarily to conceive of him as existingexisting

D.D.Therefore, to say “God does not exist” is to contradict oneselfTherefore, to say “God does not exist” is to contradict oneself

E.E.Therefore, the sentence “God exists” is necessarily trueTherefore, the sentence “God exists” is necessarily true

Therefore: We can be certain that God existsTherefore: We can be certain that God exists


III – The Existence of Physical SubstanceIII – The Existence of Physical Substance

We can doubt the existence of the world and external objects because:We can doubt the existence of the world and external objects because:a)a) We might be dreamingWe might be dreamingb)b) A demon might be deceiving us (similar to A demon might be deceiving us (similar to The Matrix)The Matrix)

But! God is incapable of deceiving usBut! God is incapable of deceiving us

All judgements that have clarity and distinctness come from GodAll judgements that have clarity and distinctness come from God

All true or certain knowledge depends on GodAll true or certain knowledge depends on God

Any errors in judgement or knowledge come from human error and not Any errors in judgement or knowledge come from human error and not GodGod

Observations:Observations:A.A.We cannot chooseWe cannot choose whether to experience an external worldwhether to experience an external world

B.B.We receive impressions from things outside of us passivelyWe receive impressions from things outside of us passively

Therefore Physical Substance ExistsTherefore Physical Substance Exists(But only because of God)(But only because of God)

DESCARTES THEORY OF REALITY


Descartes’ Theory of Reality (Reprise)Descartes’ Theory of Reality (Reprise)

We can be certain that reality is composed of two distinct substancesWe can be certain that reality is composed of two distinct substances

Physical and Mental SubstancesPhysical and Mental Substances

Each substance exhibits the following properties:Each substance exhibits the following properties:

Substance Physical(Res Extensio)

Mental(Res Cogitans)

Essence Extension Thought

Modes Size Affirmation

Shape Denial

Location Doubt

Part Volition

Mobility Hope

Lecture 6: Descartes

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