PHIL 151 History of Modern Philosophy

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PHIL 151 History of Modern Philosophy

• Dr. Martin Godwyn
• Fall 2008
• WEEK 3 Descartes Ontology

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Why prove the existence of God?

• Why does Descartes need to prove the existence of
  God?
• Having admitted that his senses and (perhaps)
  even elementary logical operations can be
  deceived by an evil demon, he needs a benevolent
  God to ensure that he is not systematically
  deceived in his reasoning or (ultimately) by his
  senses.
• Thus, he needs to prove that what he clearly and
  distinctly conceives by the natural light of
  reason will be reliable.

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Why prove the existence of God?

• In the Fourth Meditation, Descartes argues that a
  benevolent God, would not allow him to be without
  at least the capability of distinguishing
  knowledge from erroneous belief, because this
  would require God to be deceitful, which
  contradicts the concept of God.
• Thus, since he clearly and distinctly conceives
  that God must exist, he knows that when guided by
  the light of reason he will not be led
  systematically astray.

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The Cartesian Circle

• Here critics say Descartes reasoning is
  circular.
• It is by application of the natural light of
  reason that he has been guided to make various
  arguments and claims, including an argument for
  the existence of a benevolent God who would not
  allow him to be systematically deceived. This
  conclusion, by means of the argument, he clearly
  and distinctly sees to be true.

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The Cartesian Circle

• But it is precisely in order to prove that what
  he clearly and distinctly sees to be true must be
  true, that he needs to prove Gods existence.
  Otherwise, the evil demon might be leading him
  astray in (amongst other things) his proof of
  God. This is often called the Cartesian Circle.
• Can Descartes escape this circle?
• Ask yourself this what is it for a belief to be
  unshakable or certain?

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Certainty normative or psychological?

• A key issue here is whether, regarding the claim
  that anything clearly and distinctly conceived of
  as being true must be true, the third meditation
  argument is intended to establish that
• a) we ought to believe it, or
• b) as a matter of psychological necessity, we
  cannot help but believe it.

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Why do we err?

• Another immediate problem (also dealt with in the
  Fourth Meditation) is that his arguments might
  prove too much.
• Clearly, we sometimes are mistaken. But how can
  this happen, given that there exists a
  non-deceiving God who would not allow us to be
  systematically mislead?

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Why do we err?

• It must be simply this the scope of the will is
  wider than that of the intellect but instead of
  restricting it within the same limits, I extend
  its use to matters which I do not understand.
  Since the will is indifferent in such cases, it
  easily turns aside from what it true and good,
  and this is the source of my error and sin.
  (21)...
• If I restrain my will so that it extends to
  what the intellect clearly and distinctly
  reveals, and no further, then it is quite
  impossible for me to go wrong. (22)

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Why do we err?

• Descartes response hinges on our wilful nature.
  We are gifted with free will, and we sometimes go
  beyond the boundaries of what reason and evidence
  can justify to believe things for which we have
  inadequate grounds. Thats when we make mistakes,
  argues Descartes.
• In short, God does not deceive us, we deceive
  ourselves by not restraining our will (with
  respect to belief) within the bounds of the
  intellect.

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Another proof of God

• The primary goal of the Fifth Meditation, is to
  offer another proof of God.
• What Descartes offers in the Fifth Meditation is
  a crisper version of what came to be called the
  ontological proof of God, more famously
  attributed to St. Anselm.

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God as necessary-existence

• Roughly, the argument goes like this
• 1. God is a supremely perfect being.
• 2. Existence is a perfection.
• 3. Therefore, existence cannot be separated from
  concept of God i.e., it is a contradiction to
  suppose a supremely perfect being without it
  existing, since to not exist would be to lack a
  perfection.
• 4. Any property that cannot be separated from
  something is necessarily a property of such an
  object.
• 5. Therefore, God necessarily exists.

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God is a supremely perfect being

• Descartes claims, as we know, to have this
  concept of God innately. But here the source of
  the concept does not matter very much for this
  proof.
• What matters, firstly, is that the concept of a
  supremely perfect being is logically coherent and
  hence is a logical possibility.
• (Note Descartes insists that God cannot do the
  logically impossible. So he avoids old chestnuts
  such as Can God make a stone so heavy even he
  cant lift it? answering either way seems to
  limit Gods powers.)

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Existence as a perfection

• The claim that existence is a perfection is
  perhaps the most critical premise.
• The underlying motivation for this seems to be
  that in some metaphysically significant sense,
  something will be a greater or more perfect thing
  if it is a real thing as well as an idea rather
  than just an idea.
• Is this an intuitively sound principle?

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Necessary existence

• It is important to note that Descartes thinks
  that the ontological argument shows that God does
  not merely exist, but necessarily exists.
• For Descartes, Gods existence is a matter of
  logical necessity flowing from the concept of
  God, just as much as having internal angles
  adding to two right angles is a necessary feature
  of triangles.
• (The mathematician, Kurt Gödel, even developed a
  formal mathematical proof of Gods existence
  based on this argument.)

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The necessity of God

• It is quite evident that existence can no more
  be separated from the essence of God than the
  fact that its three angles equal two right angles
  can be separated from the essence of a triangle,
  or than the idea of a mountain can be separated
  from the idea of a valley. Hence it is just as
  much of a contradiction to think of God (that is,
  a supremely perfect being) lacking existence
  (that is, lacking a perfection), as it is to
  think of a mountain without a valley. (24)

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Criticisms

• There are a number of criticisms of the
  ontological proof for God.
• 1. You cant define things into existence.
• Descartes agrees, but responds that the internal
  angles of a triangle adding to two right angles
  is not a matter of mere definition its a
  logical necessity. We dont define triangles
  having those internal angles, its just a
  necessary truth about them. And the existence of
  God is just like that a necessary property of
  God.

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Is existence a property?

• 2. Existence is not a property attributable to
  things.
• Kant argues that existence is not, properly
  speaking, a property of things in the relevant
  sense, hence not a perfection.
• Existence is more like a precondition for the
  possibility of something having properties at all.

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Sixth Meditation

• In the Sixth Meditation Descartes applies his
  results to show that
• 1. material bodies exist out in an external
  world, and
• 2. there are two basic and mutually exclusive
  kinds of stuff in the universe mind and body.

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The external world

• Descartes argues that sensation can only give me,
  at best, a probabilistic justification for the
  existence of an external world.
• Using the example of a thousand-sided figure, he
  notes that perception and our faculty of the
  imagination that utilises it, is often confused
  and indistinct. By contrast, the conception of a
  thousand-sided figure is as clear and distinct
  for a thousand-sided as for a pentagon.

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The external world

• Using his faculty of understanding, he then
  argues that
• God has given me no faculty at all for
  recognising any such source for these
  perceptual ideas on the contrary, he has given
  me a great propensity to believe that they are
  produced by corporeal things. So I do not see how
  God could be understood to be anything but a
  deceiver if the ideas were transmitted by a
  source other than corporeal things. It follows
  that corporeal things exist. (29)

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Mind and Body

• Descartes arguments also lead him to conclude
  that there is an essential metaphysical
  distinction between the mind and the body.
• This view Cartesian Dualism claims that there
  are two fundamentally distinct kinds of stuff in
  the universe matter and mind.
• Cartesian Dualism, and the challenges it faces,
  generates a great deal of philosophical enquiry
  through to the present day.

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Physicalism

• Cartesian Dualism can be contrasted with a number
  of other positions
• Physicalism (materialism) The view that the only
  substance that exists fundamentally is matter or
  physical stuff. The mental is nothing over and
  above the physical.
• Not a very popular view until the 19th and 20th
  century. (Although Thomas Hobbes, a contemporary
  of Descartes, was an early advocate).

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Idealism

• Idealism The view that the only thing that
  exists is mental stuff minds and the ideas they
  contain. Matter and all things physical is
  nothing over and above the mental. Berkeley is
  the chief advocate of this view.
• Both idealism and physicalism are monisms they
  claim that there is just one basic kind of stuff
  in the universe.

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Neutral Monism

• Some monisms deny that that all that exists is
  one of those two kinds. Instead, they suggest
  that mind and matter is really just two
  attributes (or ways of being) of a single
  substance.
• The physical and the mental are not kinds of
  stuff, on this view, but rather ways that stuff
  has of being or presenting itself to us. This
  view is often called neutral monism, and is
  represented by Spinoza.

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Why dualism?

• Descartes argues that mind (i.e., I, the self,
  the soul) and matter (i.e., material body or
  corporeal stuff) must be different kinds of
  substance.
• He presents two closely related arguments for
  this view that flow into each other
• 1. The argument from conceivable separation I
  can conceive of the (mind) without (body).
• 2. The argument from essential properties what
  is essential to each is the contradictory of what
  is essential to the other.

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The argument from conceivable separation

• The argument from conceivable separation draws on
  a key result of his skeptical arguments in the
  first two meditations.
• The fact that I can clearly understand one thing
  apart from another is enough to make me certain
  that the two things are distinct, since they are
  capable of being separated, at least by God. (28)

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The argument from conceivable separation

• In essence, the argument seems to be this
• 1. I can conceive of mind existing without body
  and body without mind.
• 2. Whatever can be separated in conception is
  (essentially) distinct.
• 3. Therefore, mind and body are (essentially)
  distinct substances.
• What do you think of this argument?

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The argument from essential properties

• 1) The mind is essentially a thinking thing. (In
  other words, thinking, which includes doubting,
  imagining, believing etc., is the essential
  property of minds. Anything that thinks is a
  mind, and anything that is a mind, thinks.)
• Simply by knowing that I exist and seeing at
  the same time that absolutely nothing else
  belongs to my nature or essence except that I am
  a thinking thing, I can infer correctly that my
  essence consists solely in the fact that I am a
  thinking thing. ... (28)

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The argument from essential properties

• 2) It is inconceivable that a thinking thing be
  divided into two. Minds are necessarily
  indivisible. (Consider what is half a thought
  or half a mind? Descartes argues that this is
  incoherent.)
• 3) For any spatially extended thing, it is
  conceivable that it be divided into two. I.e.,
  spatially extended things are necessarily
  divisible, at least in principle.
• 4) Therefore, minds cannot be spatially extended.

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The argument from essential properties

• 5) A body is essentially a spatially extended
  thing. (From the ball of wax argument anything
  that is a body has spatial extension, and
  anything spatially extended is a body.)
• 6) Therefore, since minds and bodies have
  essential properties that are inconsistent with
  each other (respectively non-extension and
  extension), minds cannot be bodies, and bodies
  cannot be minds.

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The argument from essential properties

• It is true that I may have ... a body that is
  very closely joined to me. But nevertheless, on
  the one hand I have a clear and distinct idea of
  myself, in so far as I am simply a thinking,
  non-extended thing and on the other hand I have
  a distinct idea of body in so far as this is
  simply an extended, non-thinking thing. And
  accordingly, it is certain that I am really
  distinct from my body, and can exist without it.
  (28)
• Do you agree?

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The attractiveness of dualism

• Dualism did not start with Descartes. Dualism was
  a background assumption of most Western thinkers
  prior to Descartes and remains a popular and
  perhaps intuitive position even today.
• But Descartes helped to bring to a focus the deep
  problems that underlie our intuitive notions of a
  world of mind and matter as fundamentally
  different kinds of stuff.

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Explaining interaction

• The central problem that Descartes faced by
  adopting dualism was how to explain the apparent
  interaction between mind and matter. For example
• Someone stabs a fork into my leg (a physical
  event) apparently causes me to feel pain (a
  mental event).
• Me thinking of sucking lemons (a mental event)
  apparently causes my mouth to salivate (a
  physical event).

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Descartes view

• Nature also teaches me, by these sensations of
  pain, hunger, thirst and so on, that I am not
  merely present in my body, as a sailor is present
  in a ship, but that I am very closely joined and,
  as it were, intermingled with it, so that I and
  the body form a unit. If this were not so, I, who
  am nothing but a thinking thing, would not feel
  pain when the body was hurt, but would perceive
  the damage purely by the intellect, just as the
  sailor perceives by sight if anything in his ship
  is broken. (29)

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The mind-body problem

• But even intermingled stuff needs to interact to
  explain apparent mind-body interaction.
  Descartes best guess was that the interaction
  took place in the pineal gland (at the base of
  the brain), but where it happens is not the real
  philosophical issue how can something extended
  or material possibly interact with something
  non-extended and non-material?
• This problem how the mental and the physical
  interact or are metaphysically related is
  usually known as the mind-body problem.