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Descartes, a priori intuition and demonstration in meditation 3

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For Phil 1 students. This powerpoint is intended to help students see that the Cogito is a good example of a foundational truth best understood as an a priori intuition

For Phil 1 students. This powerpoint is intended to help students see that the Cogito is a good example of a foundational truth best understood as an a priori intuition

Published in: Spiritual, Health & Medicine

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  • 1. The Cogito: An a priori intuition, demonstration?
  • 2. Descartes’ Cogito: Intellectual Intuition?
    • We will consider the Cogito again…
      • Is it an inferential argument, a tautology, an intellectual intuition?
      • If it is an intellectual intuition,
        • can it ground and justify Descartes’ fundamental claims about what exists?
        • or might it (only) justify less substantial claims?
        • or might it be wholly mistaken?
    • Please turn to your copy of the text…
  • 3. Could the Cogito be an inference?
    • A deductive syllogism is an inferential argument of the form:
      • ‘ All As are Bs  ‘Major Premise’
      • ‘ X is an’ A  ‘Minor Premise’
      • ‘ therefore X is a B’  conclusion
    • (Famous) example:
      • All men are mortal
      • Socrates is a man
      • Therefore Socrates is mortal
    • Could ‘I think, therefore I am’ be a ‘deductive syllogism’?
  • 4. Could the Cogito be an inference?
    • If it were an inference, it would not be an intellectual intuition…(why?)
    • But: if it is an inference, what is Descartes’ Major Premise?
    • Task: rewrite the Cogito as a deductive syllogism
    • … what is Descartes’ Major Premise?
  • 5. Could the Cogito be an inference?
    • MP = The general proposition ‘All thinking things exist’
      • But Descartes has resolved to doubt all general propositions…
      • So he has not proved that all thinking things exist…
        • (and do all thinking things exist? What of fictions, angels?)
      • So he can’t have his major premise yet…
    • Hence, the cogito argument cannot be an inferential argument (that succeeds)
  • 6. Could the Cogito be an analytic truth?
    • Is the Cogito (merely) a tautology?
      • Does Descartes think that the concept of my present existence is contained within that of my thinking?
      • (Is it clear that it is?)
    • Were this to be so, while the cogito would be indubitable, it would also be empty.
      • Nothing could follow from it…
      • … it would not be a good foundation for knowledge…
      • … it would not be useful, particularly…
    • It would be an analytic truth not an intellectual intuition…
  • 7. The Cogito: a Self-Verifying Thought?
    • He actually writes ‘I am, I exist , must be true, whenever I utter or conceive it in my mind ’.
      • Its truth becomes apparent through the act of performing it: ‘I am thinking , therefore I exist.’
    • Descartes does indeed also suggest this elsewhere:
      • “ When someone says “I am thinking therefore I am, or I exist”, he…recognises it as something self-evident by a simple intuition of the mind.”
    • So, Descartes intends the Cogito to be a self - verifying act of intellectual intuition.
    • It is often called his ‘First Certainty’ for this reason.
  • 8. Issues with Descartes’ intellectual intuition: if true, time limited
    • The Cogito is a very limited proof: ‘ I am, I exist , must be true, whenever I utter or conceive it in my mind ’.
    • Isn’t he admitting that you only exist for as long as you are performing the Cogito?
    •  ‘ It will be true only if I think it and only so long as I think it. ‘
    • So, the proof of self-existence expressed by the cogito is temporary…
      • But Descartes thinks that even a single moment is enough…
    Rene Magritte, ‘The Blank Chart’, 1961
  • 9. Issues with Descartes’ intellectual intuition: Humean bundles, limited selves
    • Can Descartes claim that he has an immediate, unmediated, non-inferential perception of himself?
    • In opposition to Descartes, David Hume says that whenever he tries to perform the Cogito, he has no certain consciousness of himself…
    • “ For my part, when I enter most intimately into what I call myself I always stumble on some particular perception or other, heat or cold, light or shade, love or hatred, pain or pleasure. I never can catch myself at any time without a perception, and never can observe anything but the perception.” ( Treatise , I,iv,6)
    • … the self is just a bundle of sensations
  • 10. Issues with Descartes’ intellectual intuition: Lichtenberg, grammar, absence of self
    • Compare
      • ‘ Eric runs’ – there is a subject, running.
      • ‘ It rains’ – is there a subject, raining?
      • ‘ Eric thinks’ – there is a subject, thinking.
      • ‘ I think’ – is there a subject, thinking?
    • Georg Lichtenberg (C18 physicist, aphorist): ‘“It thinks”, we really ought to say, just as we say, “It thunders”’.
    • We assume the sentence ‘I think’ has a subject…does it?
  • 11. Intellectual intuitions summarised…
    • Descartes thinks that the Cogito is a moment of pure a priori intuition or demonstration…
      • His Archimedean Point
      • The foundational, non-inferential justification-condition which allows a key knowledge-claim to be made…
    • But there are some key problems with the Cogito:
      • Arguably it is a proof only of flashes of self-existence
      • Arguably it does not prove the existence of a classically conceived self or ego
    • Still, Descartes thinks that Fundamental Claims about what exists can be grounded in and justified by a priori intuition and/or demonstration.
  • 12. The Cogito as an Archimedean Point: Clear and Distinct ideas
    • Even if the Cogito is only performed for an instant it is indubitably true whilst it is being performed.
    • It is a ‘clear and distinct idea’ and
      • “ If we give assent only to those things which we clearly and distinctly perceive, we will never accept anything false as being true…".
      • “ I call 'clear' that perception which is present and manifest to an attentive mind…”
      • I call 'distinct', that perception which, while clear, is so separated and delineated from all others that it contains absolutely nothing except what is clear“.
    • So the clear and distinct perception of an idea means (for Descartes) that it must be true.
  • 13. The Clear and Distinct Idea of God
    • Another clear and distinct idea we have is that of God
      • We have the idea of God within us
      • He has placed his ‘trademark’ on us.
    • Ideas are copies of originals which are greater still. And a trademark implies a maker.
    • So God must exist, to have originated the idea of him / to have placed his trademark.
    • And God is not a deceiver: so anything we perceive clearly and distinctly is true.
    • [There is a circularity here…the Cartesian Circle…can anyone spot it?]
    • So we can trust our senses if we check our sensory experience using our rational intellect…
  • 14. The Wax Example: rationally judging one’s senses
    • Match the statements below to Descartes’ text in your handout. They are not in the right order…
    • Descartes points out that if all of the sensory properties of the melted wax are quite different to the solid wax, we cannot know through our senses that it is the same wax.
    • Descartes takes a really good common example of something that people think they know about through their senses – wax. He lists its sensory properties – all are really obvious ones.
    • Descartes’ conclusion is that even bodies, material things, are really known certainly only by the mind alone .
    • Next Descartes reminds us that wax melts and all of its physical properties change really easily. But we’d still know it was the same wax. How?
    • So if the wax isn’t ultimately known through the senses – or the imagination – then what’s the alternative? The wax must ultimately be known to us by the mind alone.
    • We might say that we ‘see’ wax (or the TV, or a friend), but really what’s going on when we see things is that we are using our mind’s power of rational judgement to rationally assess confusing sensations (we actually see a cloak and a hat going past outside our window, for example, but we rationally conclude that there is a person there).
  • 15. The Wax Example: Answers
    • Descartes takes a really good common example of something that people think they know about through their senses – wax. He lists its sensory properties – all are really obvious ones.
    • Next Descartes reminds us that wax melts and all of its physical properties change really easily. But we’d still know it was the same wax. How?
    • Descartes points out that if all of the sensory properties of the melted wax are quite different to the solid wax, we cannot know through our senses that it is the same wax.
    • We might say that we ‘see’ wax (or the TV, or a friend), but really what’s going on when we see things is that we are using our mind’s power of rational judgement to rationally assess confusing sensations (we actually see a cloak and a hat going past outside our window, for example, but we rationally conclude that there is a person there).
    • So if the wax isn’t ultimately known through the senses – or the imagination – then what’s the alternative? The wax must ultimately be known to us by the mind alone.
    • Descartes’ conclusion is that even bodies, material things, are really known certainly only by the mind alone .
  • 16. So:
    • Is certainty confined to the tautological?
      • How useful are tautological statements?
      • Are there synthetic a priori ideas?
      • How useful are synthetic a posteriori ideas?
    • Is certainty confined to introspection?
      • Is introspection certain?
      • Could other justifications of knowledge be certain?
    • Might some claims about what exists or what occurs be justified by sensory experience?
    • ..to Hume are we speaking…