Descartes Meditations II & III. Phil 100, Intro to Philosophy Benjamin Visscher Hole IV

Transcription

1 Descartes Meditations II & III Phil 100, Intro to Philosophy Benjamin Visscher Hole IV

2 SUMMARY OF MEDITATION ONE 1. Knowledge is either a priori or it is a posteriori. 2. If it is a posteriori, we do not have it (because of the dreaming argument). 3. If it is a priori, we still do not have it (because of the evil deceiver argument). 4. Therefore, we do not have knowledge. WE DON T KNOW ANYTHING!

3 Structure of the Meditations Meditation I Doubt everything I can find any reason to doubt in order to provide a foundation for knowledge Meditation II Prove that there are no grounds to doubt that I exist (qua thinking being) Meditation III Prove God both exists and does not deceive us

4 EVIL DECEIVER ARGUMENT 1. ED is possible. 2. If ED is possible, I cannot rule out that he is not actual. 3. If I cannot rule out that he is not actual, then my beliefs of reason are dubitable. ED calls all of my beliefs into question!!

5 Meditation 2 It is as if I had suddenly fallen into a deep whirlpool; I am so tossed about that I can neither touch bottom with my foot nor swim up to the top Just so, great things are also to be hoped for if I succeed in finding just one thing, however slight, that is certain and unshaken (49).

6 Knowledge=Justified True Belief Someone (S) knows K if and only if: 1. S believes K. 2. K is true. 3. S is justified in believing K.

7 Knowledge=Justified True Belief

8 Does K really = JTB? Jones is a zoo keeper. Unfortunately, his zoo has been losing a lot of money with the recent economic recession. Even more unfortunately, many of the zebras have died. Luckily, Jones is also an expert make-up artist and special effects wiz. So Jones hatches a scheme to stay in business. He buys old race horses on their way to the glue factory. He then paints the horses black and white. Well, Jones does an excellent job and successfully deceives the patrons of his zebra exhibit. One day, Smith decides to visit the zoo. He believes that he sees zebras in the exhibit when he in fact sees horses. Of course, although Smith only sees the cleverly disguised zebras, there are real zebras somewhere in the exhibit. Adapted from Dretske, F., 1970, Epistemic Operators, Journal of Philosophy, 67: Does Smith know that there are zebras in the exhibit?

9 Knowledge=Justified True Belief Someone (S) knows K if and only if: 1. S believes K. 2. K is true. 3. S is justified in believing K.

10 When is S justified in believing K? Does S s being justified require that: (a) there are good reasons that account for being right about K OR (b) S has good reasons for being right about K?

11 Internalism vs. Externalism Does S s being justified require External Justification There are good reasons that account for being right about K. E.g, S has a (certain kind of) causal explanation for K. Internal Justification - S has good reasons for being right about K. - E.g., S has a successful rationalization for K.

12 Mr. Truetemp Suppose a person, whom we shall name Mr. Truetemp, undergoes brain surgery by an experimental surgeon who invents a small device which is both a very accurate thermometer and a computational device capable of generating thoughts. The device, call it a tempucomp, is implanted in Truetemp s head so that the very tip of the device, no larger than the head of a pin, sits unnoticed on his scalp and acts as a sensor to transmit information about the temperature to the computational system of his brain. This device, in turn, sends a message to his brain causing him to think of the temperature recorded by the external sensor. Assume that the tempucomp is very reliable, and so his thoughts are correct temperature thoughts. All told, this is a reliable belief-forming process. Now imagine, finally, that he has no idea that the tempucomp has been inserted in his brain, is only slightly puzzled about why he thinks so obsessively about the temperature, but never checks a thermometer to determine whether these thoughts about the temperature are correct. He accepts them unreflectively, another effect of the tempucomp. Thus, he thinks and accepts that the temperature is 104 degrees. It is. Does he know that it is? From Keith Lehrer s Theory of Knowledge (1990)

13 Mr. Truetemp Externalism: S is justified if there s any sort of good explanation (including a causal explanation). Mr. Truetemp is a reliable indicator of the temperature. Would you say that he knows the temperature?

14 Meditation 2 It is as if I had suddenly fallen into a deep whirlpool; I am so tossed about that I can neither touch bottom with my foot nor swim up to the top Just so, great things are also to be hoped for if I succeed in finding just one thing, however slight, that is certain and unshaken (49).

15 Foundationalism Not all justification can be transmitted from beliefs to beliefs. Some have to be justified not on the basis of any others. Need some belief that we can be sure is justified. Call this a basic belief. Foundationalism: A belief is justified iff it is a basic belief or justified on the basis of another justified belief (or beliefs).

16 Basic Beliefs Self-justifying beliefs? A belief is self-justifying iff the mere fact that you believe it is enough to guarantee that it is true. Descartes, Cogito ergo sum I think, therefore I exist. If you believe that you are thinking, then you are thinking (believing is a kind of thinking). An the mere fact that you are thinking implies that you exist. There must be a you that is thinking! This is true, according to Descartes, even if we re BIVs! A belief is basic if you cannot be mistaken about it if it is certain.

17 The Cogito Thus, after everything has been most carefully weighed, it must finally be established that this pronouncement I am, I exist is necessarily true every time I utter it or conceive it in my mind (50).

18 The Cogito Editors Discussion Question One question is whether Descartes' insight really takes the form of an argument There is little doubt about the cogency of this inference, but the obvious question is why the premise [ I think ] is justified. Could the evil genius deceive me about the truth of this premise? Why or why not? Or is it perhaps a mistake to think of the Cogito as an argument at all, rather than just one unitary insight? And what exactly would that insight be? (63)

19 The Cogito 1. All my beliefs (both a priori and a posteriori) are dubitable. 2. If I were doubting that I am doubting right now, then I would be doubting. 3. Doubting is a form of thinking. 4. Thinking requires existence. 5. I think therefore, I am.

20 The Cogito It seems that basic beliefs cannot be beliefs about the world. How could you be certain of anything about the world, given the BIV scenario? Given ED?! Is the Cogito s justification for one s existence a priori or a posteriori? Internal or external? Is If I think, then I exist a necessary truth? Is it an analytic truth? Explain.

21 The Cogito 1. All my beliefs (both a priori and a posteriori) are dubitable. 2. If I were doubting that I am doubting right now, then I would be doubting. 3. Doubting is a form of thinking. 4. Thinking requires existence. 5. I think therefore, I am.

22 Res Cogitans I am a thinking thing What then did I [formerly] think I was? (50) How could I in principleknow about the existence of bodies (material substances)?

23 The Wax Argument How could I in principle- have knowledge of bodies? 1. Either we have knowledge through the senses, the imagination or through the intellect (reason) alone. 2. We can t have it through the senses 3. We can t have it though the imagination 4. It must be the intellect

24 The Wax Argument 1. The wax appears to have certain properties (color, scent, size, shape, hardness, and coldness). 2. But these properties change without the wax ceasing to be what it is. (E.g., when it is held to a flame.) 3. Nevertheless, the wax appears to remain a flexible and extended body (regardless of the properties I perceive). 4. I cannot imagine all the possible changes (extensions) the wax could undergo. 5. Therefore, the wax can be extended in ways that I cannot accurately imagine.

25 The Wax Argument Rationalism For since I now know that even bodies are not, properly speaking, perceived by the senses or by the faculty of imagination, but by the intellect alone, and that they are not perceived through their being touched I manifestly know that nothing can be perceived more easily or evidently than my own mind. (52)

26 The Wax Argument Rationalism How could I in principle- know about the existence of bodies (material substances)? Not perception Not imagination Intellect/Reason

27 The Wax Argument How can we have knowledge of bodies? 1. Either we have knowledge through the senses, the imagination or through the intellect (reason) alone. 2. We can t have it through the senses 3. We can t have it though the imagination 4. It must be the intellect

28 Descartes Meditation Three

29 Transition Editors summary of Meditation Two: I can know that I am thinking and also that I am thinking (experiencing, doubting, wondering) about various things, but not that anything beyond myself and my own conscious states exist (53).

30 Clear and Distinct Ideas Justification Descartes: This is owing to the fact that there can be no other faculty that I can trust as much as this light and which could teach that these things are not true Editors: By the natural light Descartes seems to mean something like a priori insight into why a claim must be true the sort of insight that is reflected in the claim seeming clear and distinct (54).

31 God: Epistemology & Metaphysics God is All-PKG / OOO. If God exists, then we don t have to worry about the existence of ED. And certainly, because I have no reason for thinking that there is a God who is a deceiver (and of course I do not yet sufficiently know whether there even is a God), the basis for doubting is very tenuous and, so to speak, metaphysical (53).

32 God: Epistemology & Metaphysics God is All-PKG / OOO. If God exists, then we don t have to worry about the existence of ED. Descartes needs to get rid of the evil deceiver (in order to have basic beliefs about things other than one s own existence). And he must do so in a way that the atheists will accept.

33 Preliminaries for the Causal Argument for the existence of God: Ideas Ideas are (a) (b) (c) Innate Adventitious Fictitious An innate idea is one that is programmed into a person at birth Ideas produced in me are fictitious. What is the third alternative? (54)

34 Preliminaries for the Causal Argument OBJECTIVE REALITY (OBJECT OF THOUGHT) & FORMAL REALITY (MIND-INDEPENDENT EXISTENCE) objective reality: reality as an object of thought formal or actual reality (reality in the ordinary sense) The labels formal and objective reality strike our contemporary ears as terminologically backwards (55)

35 Preliminaries for the Causal Argument: The Causal Principles The Causal Principles (CP1) Everything that comes into being has a cause. (CP2) The cause of anything that comes into existence must at least have as much formal reality as that which it caused. (CP3) The cause of anything with objective reality must have at least as much formal reality that thing has objective reality.

36 The Causal Argument for the existence of God The Causal Argument for God 1. I have a clear and distinct idea of God (all-pkg/ OOO). 2. This idea must have a cause. This is because of (CP1). 3. This cause has more objective reality than any of my ideas. 4. (CP2) The cause of anything that comes into existence must at least have as much formal reality as that which it caused. 5. (CP3) The cause of anything with objective reality must have at least as much formal reality that thing has objective reality. 6. Therefore, God exists.

37 The Causal Argument for the existence of God Editors Question isn t Descartes arguing in a circle by assuming that we can trust metaphysical principles before establishing that God exists? (57)

38 Meditation Five: The Ontological Argument for God s existence The Ontological Argument 1. I have clear and distinct idea of God. 2. God is All-PKG/OOO. 3. Necessary existence is perfection. 4. The idea of God is an idea of existence. 5. Therefore, God exists necessarily.

39 The Cartesian Circle The broader argument that unfolds has seemed to many readers to be viciously circular the so-called Cartesian Circle. Descartes first argues from clearly and distinctly perceived premises to the conclusion that a non-deceiving God exists; he then argues from the premise that a non-deceiving God exists to the conclusion that what is clearly and distinctly perceived is true. The worry is that he presupposes the C&D Rule in the effort to prove the C&D Rule. SEP:

40 The Cartesian Circle Did Descartes play the ole switcheroo on us? Meditation One Justification depends on Method of Doubt vs. Meditation Three Justification depends on the C&D Rule

41 The Wax Argument & The C&D Rule Rationalism For since I now know that even bodies are not, properly speaking, perceived by the senses or by the faculty of imagination, but by the intellect alone, and that they are not perceived through their being touched I manifestly know that nothing can be perceived more easily or evidently than my own mind. (52)

42 Plato s Imperfection Argument (Phaedo 74-76)? Descartes (Meditations III, HR I, 166): For how would it be possible that I should know... that something is lacking in me, and that I am not quite perfect, unless I had within me some idea of a Being more perfect than myself, in comparison with which I should recognize the deficiencies of my nature? The structure of the argument is the same as Plato s: 1. I judge myself to be imperfect. 2. That is, I judge myself to lack perfection. 3. Hence, I have the idea of perfection. 4. Hence, there is a being that this idea is an idea of. From S. Marc Cohen, Professor Emeritus, University of Washington: <

43 Knowledge=Justified True Belief Someone (S) knows K if and only if: 1. S believes K. 2. K is true. 3. S is justified in believing K.

44 Foundationalism Foundationalism: A belief is justified iff it is a basic belief or justified on the basis of another justified belief (or beliefs). Question-Begging Problem: What justifies basic beliefs?

45 Evidentialism Evidentialism: S is justified in believing K if and only if S has sufficient evidence E for K. Infinite regress problem: In order to believe K, it needs to be based on E. But in order to believe E, it needs to be based on some other beliefs. Which need to be based on some others this seems to lead to an infinite regress.

46 Reliabilism Reliabilism: S is justified in believing K if and only if K is formed through a reliable belief forming process. Question Begging Problem? Infinite Regress Problem?

47 Coherentism One way to avoid the infinite regress: A based on B, B based on C, C based on D, D based on A. A is justified. Coherentism: Justification results from the whole system of beliefs. K is justified iff it belongs to a consistent and coherent system of mutually supporting beliefs.

48 Coherentism S is justified in believing K is justified iff it belongs to a consistent and coherent system of mutually supporting beliefs. Question-begging worry?

49 Knowledge=Justified True Belief Someone (S) knows K if and only if: 1. S believes K. 2. K is true. 3. S is justified in believing K. Which theory presents the best account of justification? (a) foundationalism (b) evidentialism (c) reliabilism (d) coherentism