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Descartes’ Skeptical Observations 1. Several years have now past since I first realized how many were the false opinions that in my youth I took to be.

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Presentation on theme: "Descartes’ Skeptical Observations 1. Several years have now past since I first realized how many were the false opinions that in my youth I took to be."— Presentation transcript:

1 Descartes’ Skeptical Observations 1. Several years have now past since I first realized how many were the false opinions that in my youth I took to be true, and thus how doubtful were all the things that I subsequently built upon these opinions. 2. Whatever I had most true I took in from the senses...; however I noticed that they sometimes deceived me.

2 Descartes’ Dreams and Demons 3. This all seems as if I do not recall having been deceived by similar thoughts in my dreams. As I consider these cases I see there are no definite signs to distinguish being awake from being asleep. 4. Suppose an evil genius has directed his entire effort to misleading me. The heavens, the air, the earth, the colors, shapes, sounds, and all external things would be nothing but deceptive games of my dreams.

3 Qualitative indistinguishability of vat experiences and sense experiences. Oh Drat, I’m a brain in a vat!

4 Cartesian Certainty At length I am forced to admit that there is nothing among the things I once believed to be true, which it is not possible to doubt, not for reasons of frivolity...but because of valid and considered arguments. Med. II: Even if a demon deceives me, “I am, I exist,” is true whenever I doubt it. No perceptual experience is required to obtain this knowledge. “My body exists” cannot be known with certainty. So I am a thinking thing that may have a body.

5 Non-sensory knowledge of body. This piece of bee’s wax: tastes sweet, smells flowery; feels hard and cold, squeezes when I press it, makes sound when I tap it. I hold it near the fire: taste is gone; smell evaporates; color changes, shape is gone; size increases, makes no sound when tapped. Yet I know it is the same wax. So my knowledge of the wax is is an intuition of the mind occasioned by (but not based on) perception.

6 Benedictus de Spinoza Method: Begin with self-evident metaphysical truths and deduce theorems implied implied by those truths, producing an absolutely certain science of reality. …[T]here cannot be conceived one substance different from another,- that is, there cannot be several substances, but one only. Extension and consciousness are modes of one infinite substance, God.

7 Leibniz ( ) The concept of extension is derivative, the building blocks of reality are psychic particles, monads. Extension is a property of a collection of particles, each of which is unextended. Each monad is designed by God to mirror the universe. They do not interact causally, but a pre- established harmony governs their behavior. A human is composed of monads, the chief of which is the soul. Principle of sufficient reason. This is the best of all possible worlds.

8 John Locke’s Empiricism If by this inquiry into the nature of the understanding, I can discover the powers thereof; how far they reach;…and where they fail us, I suppose it may be of use with the busy mind of man, to be more cautious in meddling with things exceeding its comprehension; to stop when it is at the utmost extent of its tether; and to sit down in quiet ignorance of those things, which, upon Examination, are found beyond the reach of our Capacities. To ask, at what time a man has first any ideas, is to ask, when he begins to perceive; having ideas and perception being the same things. He that would not deceive himself ought to build his hypothesis on matter of fact. An Essay Concerning Human Understanding (1690)

9 Locke’s Causal Theory of Perception, Truth, and Knowledge The perception of external objects and events causes images (ideas) in the mind; reflection on how the mind responds to this data causes ideas of another sort (belief, hope, fear). A tabula rasa (without innate ideas) acquires and sorts images, creates abstractions, and utters propositions.

10 The Production of Ideas An apple has qualities that produce the simple ideas of red, sweet, crisp; from which we form the complex idea of apple, which, when compared with other ideas, gives rise to even more abstract ideas of fruit, taste, and nutrition. Only primary qualities (extension, number, figure, motion, solidity) are real, inseparable properties of objects. Secondary qualities (color, taste, smell, sound) are produced in our minds but do not really exist out there.

11 Options in Modern Philosophy Dualism (Descartes) Materialism (Locke*) Occasionalism (Malebranche) Idealism (Berkeley): Esse est percipi; to be is to be perceived. There is no such thing as (what philosophers call) material substance.

12 The materialist world view. Physical objects would continue to exist even if there were no minds. Physical objects cause ideas to arise in our minds. Physical objects have primary qualities and secondary qualities. It is impossible to prove beyond all doubt that the physical world exists. Skepticism is irrefutable (but it may be ignored)

13 George Berkeley ( ) My endeavors tend only to unite, and place in a clearer light, that truth which was before shared between the vulgar and the philosophers: the former [holding] that those things they immediately perceive are the real things; and the latter that the things immediately perceived, are ideas which exist only in the mind. Which two notions put together constitute...what I advance.

14 Idealism Things we call substances are really just collections of ideas which depend for their existence on the mind. Reality is a community of spirits. We perceive ideas, so if we perceive objects, objects are ideas. If they weren’t ideas, we couldn’t perceive them. Since ideas are mind dependent, so must objects be.

15 Refutation of Secondary Quality Realism. Intense heat = pain. Pain is mind- dependent.  Intense heat is mind- dependent. Place cold left hand and warm right hand in water. Is the water cool or warm? Reducing sound to vibrations implies that sound is not heard.

16 Against Primary Quality Realism Red and purple sunset- is the color in the clouds? What is the real color? Sunlight? candlelight? Under the microscope? Reducing color to matter and motion makes real color invisible. Perceptual relativity affects primary quality perception as well. How large is a Perseae mite’s foot? To a mite----medium. To us tiny. To a Sub-mite--- HUGE!

17 David Hume ( ) We find in our minds impressions (direct sensations) and ideas (copies of impressions). Meaningful ideas can be traced back to the impressions that produced them. Ideas without impressions are meaningless (e.g. substance, self, cause). Legitimate ideas refer either to relations among ideas (math, logic) or to matters of fact (always possibly false). The gazing populace receive greedily, without examination, whatever soothes superstition, and promotes wonder.

18 Cause and effect. Reasoning about matters of fact assumes causal connections. But there are no impressions of causality. Sensation discovers only constant conjunction of event pairs (fire, heat). Hence, custom or habit (not knowledge) is the source of our belief in causal connections. Experience only teaches us how one event constantly follows another, without instructing us in the secret connexion which binds them together.

19 Immanuel Kant ( ) What has hitherto been called metaphysics cannot satisfy any critical mind, but to forego it completely is impossible; therefore, a critique of pure reason must be attempted. All knowledge begins with experience, but not all knowledge arises out of experience. Impressions supplied by sensation are structured by cognition. A Copernican revolution in Philosophy.

20 Is Synthetic apriori knowledge possible? Analytic statements: Content of the predicate is contained in the subject. (Nuns are female) Synthetic statements: Content of the predicate goes beyond content of the subject. (Nuns are nice) Apriori knowledge: Independent of sense experience. Aposteriori knowledge: Dependent on sense experience. Noumena: Perceiver independent reality. Phenomena: Reality as it appears to us.

21 Midterm Review Pt I. Matching. Match the philosopher with his quote: Thales, Democritus, Parmenides, Heraclitus (wk 1),Socrates (wk 2), Aquinas, (wk 3) Hume, Mill, Pascal, James (wk 4) Part II. Short answer. 1.Objection to piety definition (Euthyphro)(2) 2. The Socratic Mission (2) 3.James- skeptical balance (4) 4.Religious ambiguity(3,4) Pt. III. Essay (a) teleological (design) argument or (b) problem of evil. Part IV. Multiple choice 1. Definitions- libertarianism, hard determinism, compatibilism. 2. Problem of evil as objection to argument for God’s existence. 3. Why Plato opposes prayer/sacrifice piety. 4. Definition of “rational agent.” 5. Why Mill thinks God is finite. 6. Heraclitus’ main point. 7. Famous Socrates quote.

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