meditations on first philosophyepisyllogism：第一哲学的沉思——episyllogism.ppt

Click to edit Master title styleClick to edit Master subtitle style*1 Meditations on First PhilosophySummary ofDescartes argumentsMeditation I1. A firm foundation for the sciences requires a truth that is absolutely certain; for this purpose, I will reject all my beliefs for which there is even a possibility of doubt, and whatever truths are left will be absolutely certain. I continued2. To this end it is not necessary to go through all my beliefs individually, since they are all based on a more fundamental belief. If there is any reason to doubt this foundation belief, then all the beliefs based on it are equally doubtful. Meditation I continued3. All my beliefs about the world are based on the fundamental belief that the senses tell me the truth. But this belief is not absolutely certain. It is at least possible that everything my senses tell me is an illusion created by a powerful being. Therefore, there is some reason to doubt my foundation belief, and thus all my beliefs about the world are doubtful; none of them can serve as the foundation for science. Meditation II1. If all my beliefs about the world are doubtful, is there any truth which can be absolutely certain? Yes. Even if all of my experience is an illusion, it cannot be doubted that the experience is taking place. And this means that I, the experiencer, must exist. 2. Since the only evidence I have that I exist is that I am thinking (experiencing), then it is also absolutely certain that I am a thing that thinks (experiences), that is, a mind. Meditation II continued3. Since I am not certain (yet) that the physical world (including my body) exists, but I am certain that I exist, it follows that I am not my body. Therefore, I know with certainty that I am only a mind. 4. I am much more certain of my minds existence than my bodys. It might seem that in fact we know physical things through the senses with greater certainty than we know something intangible like the mind. Meditation II continuedBut the wax experiment demonstrates that the senses themselves know nothing, and that only the intellect truly knows physical things. It follows that the mind itself is known with greater certainty than anything that we know through the senses. Meditation III1. Every idea must be caused, and the cause must be as real as the idea. If I have any idea of which I cannot be the cause, then something besides me must exist. 2. All ideas of material reality could have their origin within me. But the idea of God, an infinite and perfect being, could not have originated from within me, since I am finite and imperfect. III continued3. I have an idea of God, and it can only have been caused by God. 4. Therefore God exists. Meditation IV1. Only an imperfect (less than perfectly good) being could practice deliberate deception. Therefore, God is no deceiver. 2. Since my faculty of judgment comes from God, I can make no mistake as long as I use it properly. But it is not an infinite faculty; I make mistakes when I judge things that I dont really know. IV continued3. God also gave me free will, which is infinite and therefore extends beyond my finite intellect. This is why it is possible to deceive myself: I am free to jump to conclusions or to proclaim as knowledge things that I dont know with absolute certainty. IV continued4. I therefore know now that if I know something with absolute certainty (clearly and distinctly), then I cannot be mistaken, because God is no deceiver. The correct way to proceed is to avoid mistakes and limit my claims to knowledge to those things I know clearly and distinctly. Meditation V1. Now I want to find what can be known for certain about material objects. Before deciding whether they exist outside me, I know that my ideas of them consist of shape, size, motion, etc. I also know that by thinking about these attributes I can discover certain facts that are necessarily true about them (the truths of geometry, for example). 2. I do not invent ideas such as geometrical shapes, nor do I get them from sensory experience. Proof of this is the fact that I can discover geometrical truths about figures which I cannot imagine. V continued3. Just as, by thinking about my ideas of geometrical shapes, I can discover truths that necessarily belong to them, I can do the same with God. I have a clear and distinct idea of a perfect being. Perfect = lacking nothing. I cannot conceive of a being that is perfect but lacks existence. Therefore, existence necessarily belongs to God. V continued4. This doesnt mean that my thinking of something makes it exist. If I conceive of a triangle, I must conceive of a figure whose angles equal two right angles. But it doesnt follow that the triangle must exist. But God is different. God, being perfect, is the one being to whom existence must belong. Thus, when I conceive of God, I must conceive of a being that exists. V continued5. Because God, being perfect, is not a deceiver, I know that once I have perceived something cle。