René Descartes The father of modern Western philosophy and the epistemological turn Methodological doubt, his dreaming argument and the evil demon argument, compared to Zhuangzi

Cogito ergo sum (Latin: "I think, therefore I am") Cogito ergo sum (Latin: "I think, therefore I am") 1. What does he mean by "think"? – thinking, doubting, feeling, sensing, willing, imagining, remembering, What does he mean by "I"? – A thinking being. Not yet include the body. 3. Can the dreaming argument or evil demon argument apply to the cogito? – No. 4. Does it prove that he exists when he is not thinking, such as when he is sleeping? – No. 5. Can I doubt my own existence? – According to Descartes: Yes -- as a mental activity, but no -- you cannot doubt it without falling into contradiction. Just like "can I get 3 from 2+2?" 6. Is Descartes proving that others do not exist? Is he saying that only he exists? – No. 7. What is the difference between the cogito and logical rules, such as A is A? – This is D's first existential judgment. 8. Why is the cogito so important? – It serves also as a proof for the reliability of reason, and the “clarity and distinctness” criteria of truth.

Is the Cogito a valid argument? Is the Cogito a valid argument? ◊ Hintikka: It is either question begging or invalid ◊ Hintikka: It is either question begging or invalid ◊ Hume: We never perceive the “self”, only bundle of perceptions ◊ Hume: We never perceive the “self”, only bundle of perceptions ◊ Gilbert Ryle: The Cartesian self is a “ghost in the machine” ◊ Gilbert Ryle: The Cartesian self is a “ghost in the machine” ◊ Wittgenstein: “I” am not part of my world, it is the limit of my world ◊ Wittgenstein: “I” am not part of my world, it is the limit of my world ◊ Buddhism: The false notion of “I” is the source of our own suffering ◊ Buddhism: The false notion of “I” is the source of our own suffering

The existence of God The existence of God 1. The Ontological Argument: (an a priori argument) God is by definition perfect Existence is a perfection God must exist 2. The “Trademark” Argument: (an a posteriori argument) (1) Everything has a cause. Nothing comes from nothing. (2) The cause must contain no less reality than its effect (the principle of causal adequacy). (3) I have the idea of an infinitely perfect Being. (4) I am imperfect, so I cannot be the cause of the idea. Only God (a perfect being) can cause such an idea in me. (5) Therefore, God exists

Is the Ontological Argument convincing? Is the Ontological Argument convincing? God is by definition perfect Existence is a perfection God must exist (1) Can I similarly define a perfect dog or island, an exista-unicorn, an exista-round-square, etc. and hence prove their existence? (2) Kant: existence is not a property. It is an instantiation. -- Existence is about "is there any X?" -- Existence is about "is there any X?" -- Property is about "what is X?" -- Property is about "what is X?"

Is the “Trademark” Argument convincing? Is the “Trademark” Argument convincing? (1) “Everything has a cause. Nothing comes from nothing.” -- Coming from nothing does not mean “caused” by nothing. -- If so, where does God come from? -- Why cannot the universe be always there? -- Modern physics: the universe may come from nothing (2) “The cause contain no less reality than its effect” (the principle of causal adequacy). -- but a murderer does not have to be as dead as his victim -- a cause only needs to be sufficient for the effect; it does not have to pre-contain the effect.

(3) “I have the idea of an infinitely perfect Being.” -- we have a concept of a perfect being, but not an idea (image) of it. (4) “I am imperfect, so I cannot be the cause of the idea. Only God (a perfect being) can cause such an idea in me.” -- why cannot the concept come from our ability to reason? (5) “Therefore, God exists” -- ?

Descartes’ Main Line of Reasoning Descartes’ Main Line of Reasoning Methodic doubt – sense experience is not reliable Cogito – (1) “I” (as a thinking being) exist. (2) Reason is the only reliable faculty for knowledge. Clarity and distinctness are the criteria for knowledge. (2) Reason is the only reliable faculty for knowledge. Clarity and distinctness are the criteria for knowledge. The Existence of God – God is not a systematic deceiver. The existence of the physical world.

Daily One-minute Paper Daily One-minute Paper 1. What is the big point you learned in class today? 1. What is the big point you learned in class today? 2. What is the main, unanswered question you leave class with today? 2. What is the main, unanswered question you leave class with today?