René Descartes (1596-1650 AD) - PowerPoint PPT Presentation

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René Descartes (1596-1650 AD)

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  1. Revised, 1/7/07 René Descartes(1596-1650 AD) Meditations on First Philosophy (1641) (Text, pp. 283-306)

  2. Anthem

  3. Background Descartes’ Problem • The problem of skepticism (D concentrates on 2 types of skepticism) • General skepticism: There are NO indubitable beliefs or propositions. • Skepticism concerning the existence & nature of the “external world”: The existence and nature of the “external world” cannot be known.

  4. The overall structure of D’s Meditations(next slide)

  5. General Cogito (existence of the “I”) (Med. I) (Med. II) Mind-Body Dualism Skepticism God (no deceiver) External 1. My idea of God (III) World 2. My contingent (Meds. III-VI) existence (III) 3. The ontological argument (again) (V) (That piece of wax)

  6. Meditation I Radical (General) Skepticism

  7. Descartes’ “Foundationalism”Epistemological Foundations & Superstructure Superstructural Beliefs (also false?) False Foundational Belief False Foundational Belief False Foundational Belief If the underlying foundations of our beliefs are false, then it is possible that all of our beliefs are false too!

  8. D’s program of radical doubt • Treat any belief that is to the slightest extent uncertain & subject to doubt just as though it is obviously false. • Accept only those beliefs that are completely certain and indubitable. • Work on the foundations of my beliefs. What are the underlying foundations of my beliefs?

  9. Foundational Beliefs(common assumptions we make) • Naïve Empiricism: True beliefs are acquired through sense experience. • My beliefs are not products of insanity. • My beliefs are not products of my dreams.

  10. Foundational Beliefs, cont’d • Physical objects: Even if we fail to perceive physical objects accurately, the “primary [measurable] qualities” of such objects (matter, extension, shape, quantity, size, location, time, etc.) are really real (i.e., physical objects do really exist). • Even if empirical beliefs are subject to doubt, mathematical propositions are indubitable (e.g., 3 + 2 = 5, a square has neither more nor less than four sides).

  11. Questions to think about: • How does Descartes challenge each of the foregoing foundational beliefs? • How does he use the ideas of God and the Devil in building his case in support of radical skepticism?

  12. Meditation II Descartes’ Refutation of Radical Skepticism

  13. Descartes’ refutation ofradical skepticism “Cogito ergo sum!” What does this mean?

  14. The most famous statement in the history of philosophy: “I think; therefore I am.” Discourse on Method (1637)

  15. “If I am deceived,then I must exist!” I cannot doubt the truth of the statement, “I exist.” I can't think that I am not thinking because then I am thinking; and if I am thinking, then I must exist. To doubt my own existence, I must exist! (Why not?)

  16. Thus, Radical (general) skepticism is refuted.

  17. Meditation II, cont’d The Mind-Body Problem & Descartes’ Psycho-Somatic Dualism

  18. Three metaphysical perspectives relevant to the “mind-body problem”

  19. Metaphysical Dualism: Reality is two-dimensional, partly material and partly non-material (minds, ideas, souls, spirits, consciousness, etc.). Metaphysical Materialism: Reality is nothing but matter-in-motion-in-space-and-in-time. There are no non-material realities. Metaphysical Idealism: Reality is nothing but Mind, Idea, Soul, Spirit, Consciousness, etc. Matter does not exist (it’s an illusion?).

  20. Application to the “mind-body problem” • Metaphysical Materialism: A person is nothing but a physical organism (body only). "Mind" (consciousness) a feature (function, epiphenomenon) of the body. • Metaphysical Idealism: A person is “consciousness only” (mind, soul, spirit); not at all a material being. • Metaphysical Dualism: A person is a composite of (1) “mind” (consciousness, intellect, soul, spirit) and (2) body.

  21. Cartesian Dualism • I know with certainty THAT “I” exist (Cogito ergo sum), but • WHAT am “I”? • Am “I” my body? No, because I can doubt the existence of my body, whereas I cannot doubt the existence of myself (the “I”). • “I” am a thinking thing, a thing that doubts, understands, affirms, denies, wills, refuses, imagines, and has sensations.

  22. Is Descartes right? Can you doubt the existence of your body (as well as other physical things)? Why or why not?

  23. “I can conceive of myself as existing without a body, but I cannot conceive of myself as existing without conscious awareness.” Bryan Magee, The Great Philosophers (Oxford 1987)

  24. Detour Descartes' piece of wax (What is this about?) D' piece of wax is a physical object. How is it known? Through the senses? Through the power of imagination? Through the intellect (judgment, intuition)?

  25. That piece of wax…. • A major dispute running through the entire history of philosophy has to do with the source(s) of human knowledge. There are two major schools: rationalism and empiricism. The empiricists hold that knowledge is derived from sense perception and experience. The rationalists (such as Descartes) hold that knowledge is derived from clear logical thinking, from the intellect (i.e., from "reason"). • In the "wax" section, which is a kind of detour from his main argument, Descartes is showing his support of rationalism. He argues that we know - through the intellect - that the wax is and remains what it is as it passes through time and change. Sense perception does not show the "substance" of the wax but only its various appearances. If we relied on sense experience rather than on "reason," then we would "know" that the wax is all of the following: cold and hard, warm and soft, hot and liquid. However, "reason" (not the senses) tells us that the substance (reality) of the wax is something more fundamental than its sensual appearances.

  26. Back to the mind-body problem…. So…in Descartes’ view, my body exists (if it exists at all) outside of my consciousness and is therefore part of the “external world.” Thus,

  27. Descartes’ mind-body dualism leads to . . . .

  28. Meditation III,which deals with (1) skepticism concerning the existence & nature of the “external world” & (2) the existence of God

  29. “I must, as soon as possible, try to determine (1) whether or not God exists and (2) whether or not He can be a deceiver. Until I know these two things, I will never be certain of anything else” (Text, 289). Why does Descartes say this?

  30. And why does Descartes think it necessary to prove the existence of God? • It's because he's looking for a guarantee that the "external world" (the world outside of his mind) is really real and not just an illusion. How does a proof of the existence of God help him with that problem? • The point is that God (who is no deceiver) guarantees that the world I perceive through my senses is really there. God authenticates my sensory experiences, thus making sensation generally reliable, not in and of itself, but because God (being perfectly good) will not allow me to be systematically deluded and deceived. • By the way, if Descartes trusted his senses, this "external world" issue would not be a problem for him. But Descartes, a "Rationalist" rather than an "Empiricist," does not trust sense experience. He needs something more than sense experience to convince him that the "external world" is real. He needs God.

  31. Descartes’ standard of certainty • What does it take for a belief to be certainly (indubitably) true? • The belief must be “clear and distinct.” (But what does this mean?) • Descartes’ general rule: “Everything that I can clearly and distinctly grasp is true.”

  32. Are the following beliefs“clear & distinct”(indubitable)? • That there are things outside myself (such as physical objects). • That these external things cause my ideas of those things in my mind. • That my ideas of external things perfectly “resemble” the things themselves. • That 3 + 2 = 5 ?

  33. Reasons for believing (1) that there are things outside myself, (2) that these external things cause my ideas of those things in my mind, and (3) that my ideas of external things “resemble” (accurately represent) the things themselves*: *The epistemology represented by (1), (2), & (3) is known as “Representationalism.”

  34. I have a strong natural inclination to believe the preceding three propositions. • My ideas of external things arise in my mind independently of my will. • It seems obvious that external objects impress their own likenesses upon my senses. (Do these reasons “clearly & distinctly” prove that Representational Realism is true?) (See 289-90)

  35. Ideas & their causes

  36. When I think of an entity, I can distinguish between . . . . • Substance (i.e., the entity itself, e.g., an automobile tire), • Modes (i.e., the ways in which the entity exists, e.g., the tire may be flat ), and • Accidents (i.e., the properties, qualities, or attributes of the entity, e.g., the color of the tire [blackness?] ). And isn’t it obvious that substance is more real than mode or accident?

  37. Ideas of things (substances, modes, accidents) must be caused to be in the mind, and the cause of any effect must be sufficient to produce its effect, i.e., there must be at least as much reality in a cause as is represented in its effect.

  38. subjective representations of the realities that cause them to be in the mind. He also believes that ideas cannot represent more reality (anything greater or more perfect) than is in the things the ideas represent. But is this last point true? Suppose I perceive an automobile with a dented fender &, from my perception, an idea of the car arises in my mind. Why can’t I think of the car as NOT having a dented fender? How might Descartes respond to this criticism? Descartes thinks of ideas as

  39. If one of my ideas • has something in it that is not within myself, then • I could not be the cause of that idea; whereas • if I could be the cause of all of my ideas, then • I will have no foolproof reason to believe that anything exists other than myself.

  40. Ideas in my mind: • of myself (could be caused by myself) • of God • of lifeless physical objects • of angels • of animals • of other people Could be composed from my ideas of myself, physical objects, and God (how?) What about physical objects?

  41. The qualities of physical objects: • Primary qualities: size, length, breadth, depth, shape, position, motion, substance, duration, number, etc. • Secondary qualities: light, color, sound, odor, taste, heat, cold, etc.

  42. Since my ideas of the secondary qualities of physical objects • are not “clear and distinct,” • and since such qualities are almost indistinguishable from nothing (i.e, they seem to represent very little reality), • I myself [a substance] could be the author of such ideas.

  43. I could also be the cause of my ideas of primary qualities. • I am a substance. • I have duration in that I exist now and have existed for some time. • I can count my several thoughts and thus the idea of number may be grounded in my thought process. • But what about my ideas of extension, shape, position, and motion?

  44. Although extension, shape, position, or motion do not exist in me (since “I” am not a physical being), these are only modes of existence, and, as a substance, “I” have more reality than these modes and “I” am therefore sufficient to cause my ideas of them.

  45. Thus, I could be the cause of my ideas of both the primary and secondary qualities of physical objects. However,

  46. I do not have what it takes to produce the idea of God (an infinite substance) from within myself (a finite substance).

  47. Descartes’ first argument for the existence of God . . . .

  48. “By ‘God,’ I mean an infinite and independent SUBSTANCE, all-knowing and all-powerful, who created me and everything else . . . . ” (Text, 291) This idea represents more reality than there is in myself (since I am finite, limited in knowledge & power, etc.). Thus, the idea of God must be caused to be in my mind by something other than myself. And . . . .

  49. since there must be at least as much reality in a cause as there is in its effect(s), it follows necessarily that my idea of God must be caused by God Himself; and if God is the cause of my idea of God, then God must exist!

  50. that I could not be the cause of the idea of God that I find in my mind since God is a being more perfect than myself. How could I, merely from within myself, form the idea of a being more perfect than myself? In that case, my idea would represent more reality than there is in its cause. Descartes’ main point here is Only God is a sufficient cause of the idea of God in my mind.