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Killing Descartes
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Killing Descartes

Timothy
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1 of 1 people found this post helpful Posted 10/11/09 - 03:17 PM: Subject: Against Descartes	#1
Let's do an exercise that could help us clarify and revisit some important concepts of modern philosophy. the exercise is to provide an argument, as simply put as possible, that shows why cartesianism is nowadays untenable. Let the variety of arguments be great, as to have views coming from not only metaphysics and epistemology, but also from ethics, religion, politics, logic, and whatnot. I'll present a classical objection to Descartes, due (If I remember correctly) to Arnauld and the Port-Royal logicians. It's actually a twofold logical objection. The main idea is that cartesianism is self-defeating. - On the first meditation, Descartes goes as far as to doubt whether certain mathematical propositions are true. It is generally agreed that this doubt encompasses not only the isolated propositions (2+2=4, etc.) but the methods by which such propositions are usually proved, i.e. deductive reasoning. Hence, deductive reasoning enters the methodical doubt as an unreliable method for establishing truth. This, however, enters into direct contradiction with Descartes' procedure, since he uses deductive reasoning throughout his meditations, including the proofs of the cogito and God's existence. Therefore, the unrestricted scope of Descartes' methodical doubt undermines his main theses. - Another objection, in the same spirit, concerns the criteria of clarity and distinctiveness to determine the truth of an idea. However, what guarantees that distinct and clear propositions yield truth? God does. But isn't Descartes using the criteria to prove God's existence? The objection is this: what is required to prove God's existence is nothing else but God's existence. A clearly circular argument, and hence untenable. Feel free to critique this argument and/or post your own. Edited by Timothy on 10/11/09 - 03:26 PM
"Neither Aristotelian nor Russellian rules give the exact logic of any expression of ordinary language; for ordinary language has no exact logic." P.F. Strawson

To Mega Therion
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Posted 10/11/09 - 03:23 PM:	#2
Hm, an objection that I've seen used against Malebranche but that applies equally well to Descartes is that the existence of bodies in their systems is unnecessary, and hence that their dualism collapses into a sort of idealism. Descartes would probably reply that God is not a deceiver, etc., but that's a weak reply at best: after all, God can hardly be held responsible for what (the existence of bodies) we conclude from our perceptions.

Arkady
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Posted 10/11/09 - 03:24 PM:	#3
Timothy wrote: On the first meditation, Descartes goes as far as to doubt whether certain mathematical propositions are true. It is generally agreed that this doubt encompasses not only the isolated propositions (2+2=4, etc.) but the methods by which such propositions are usually proved, i.e. deductive reasoning. Hence, deductive reasoning enters the methodical doubt as an unreliable method for establishing truth. This, however, enters into direct contradiction with Descartes' procedure, since he uses deductive reasoning throughout his meditations, including the proofs of the cogito and God's existence. Therefore, the unrestricted scope of Descartes' methodical doubt undermines his main theses. Timothy, This is very interesting point. You are saying Descartes's argument against deduction is self-defeating because it itself uses deduction. But, don't arguments trying to justify deduction suffer from problems of their own, in that they are circular in nature, since they employ deduction to justify deduction? I know I am far from the first person to make this point; I've just never seen a good answer to it. Edited by Arkady on 10/11/09 - 03:50 PM
"Sit down before fact like a little child, and be prepared to give up every preconceived notion. Follow humbly wherever and to whatever abyss Nature leads, or you shall learn nothing." -T.H. Huxley

Timothy
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Posted 10/11/09 - 03:38 PM:	#4
Arkady wrote: You are saying Descartes's argument against deduction is self-defeating because it itself uses induction. But, don't arguments trying to justify deduction suffer from problems of their own, in that they are circular in nature, since they employ deduction to justify deduction? I know I am far from the first person to make this point; I've just never seen a good answer to it. You mean "deduction" instead of "induction", right? Indeed, arguments trying to justify deduction tend to be based on deductive reasoning (see the thread "Completeness of Deduction" in the Logic forum for a paper of S. Haack on that issue). Even thou some have dared on to say that there are evolutionary advantages to deduction, and try to justify its validity from a naturalistic POV... but yeah, I also remain unconvinced. But the problem with Descartes is that he didn't sought to make a case against deductive reasoning. There's not a line in the Meditations that explicitly states the fallibility of deduction. The problem is that he accidentally smuggles his doubt into deductive reasoning by doubting about mathematical propositions, and hence their method of proof. No doubt Descartes, being the mathematician that he was, considered deductive reasoning as the only possible valid reasoning. Yet despite cherishing it, he ended up undermining it... perhaps a classic case of throwing away the baby with the water. To Mega Therion wrote: ...is that the existence of bodies in their systems is unnecessary, and hence that their dualism collapses into a sort of idealism. Hmm ok, but perhaps a different argument establishing the necessity of distinguishing between res cogitans and res extensa can be made via the cogito, since what the cogito supposedly proves is that there's res cogitans, but not res extensa, and hence there must be a fundamental, ontological difference between the two... Edited by Timothy on 10/11/09 - 03:46 PM
"Neither Aristotelian nor Russellian rules give the exact logic of any expression of ordinary language; for ordinary language has no exact logic." P.F. Strawson

To Mega Therion
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Posted 10/11/09 - 04:00 PM:	#5
Timothy wrote: Hmm ok, but perhaps a different argument establishing the necessity of distinguishing between res cogitans and res extensa can be made via the cogito, since what the cogito supposedly proves is that there's res cogitans, but not res extensa, and hence there must be a fundamental, ontological difference between the two... Well, yes, but it doesn't follow that any res extensa actually exists. After all, it follows from eg. Spinoza's axioms that any two attributes can be distinguished, but this doesn't establish which of them exist. A related problem with Cartesian ontology is that according to Descartes the essence of bodies is extension; bodies are simply that which is extended. But are not our perceptions (or in Descartes' terminology, 'ideas') also extended? And ideas are supposed to be modes of the soul, which Descartes defines as that which thinks, explicitly excluding extension from it.

Timothy
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Posted 10/11/09 - 04:04 PM:	#6
Ok, I see now. Good objection indeed. The proof of the external (extensional) world in Descartes does indeed rest on the fact that God guarantees it to exist. To Mega Therion wrote: But are not our perceptions (or in Descartes' terminology, 'ideas') also extended? I guess he's guilty of not being very explicit in distinguishing empirical perception (hearing, seeing, etc) from the mind's ideas.
"Neither Aristotelian nor Russellian rules give the exact logic of any expression of ordinary language; for ordinary language has no exact logic." P.F. Strawson

To Mega Therion
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Posted 10/11/09 - 04:12 PM:	#7
Timothy wrote: I guess he's guilty of not being very explicit in distinguishing empirical perception (hearing, seeing, etc) from the mind's ideas. Well, even if he did make the distinction (as some later Cartesians, Malebranche again being a case in point) the problem would remain. Because it seems to me that he is forced either to (1) regard perceptions (by which I mean the data of consciousness; in the case of visual perception a piece of extension 'filled' with a certain colour-qualia, so to speak) as bodies; or (2) deny that perceptions are extended.

treemanshope
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Posted 10/12/09 - 12:13 PM:	#8
Certainly perception is not just light falling on the retina. The nervous system is a closed system. Perception has more to do with the internal mental states of the brain than what gets into it. We are coherent of our history. We doen't have a science of nature but rather a science of mans knowledge of nature.
The words of peace are just words, it is man that gives them flesh. Bring peace into the material world. Or, bring something else. treemanshope.

To Mega Therion
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Posted 10/12/09 - 12:24 PM:	#9
Uh, come again? I never mentioned the light falling on our retina; all I mentioned is that it is quite obvious that our perceptions are extended. The image of a laptop screen that is currently in my mind, for example, clearly (and distinctly, while we're on the subject of burying old Rene) has two dimensions of extension; I could imagine a dot somewhere in the image and then imagine it moving around in two independent ways.

Tobias
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Posted 10/12/09 - 12:44 PM:	#10
This, however, enters into direct contradiction with Descartes' procedure, since he uses deductive reasoning throughout his meditations, including the proofs of the cogito and God's existence. I think defending Descartes is a more noble enterprise than killing him. Indeed many objections are difficult for him so I think it is more worthwhile to look at what still lives in Descartes. He would reply that the cogito is not a result of deductive reasoning. He replied that it was an immediate realisation. This doctrine became known as 'intellectual intuition'. He doesn't think "I think therefore I am", he realises it and upon examination, no objection can shake it, well according to Descartes. The proof of God is more problematic because he uses indeed a form of deductive reasoning, Anselm's ontological proof of God for instance. So the question is, does Descartes' system survive without God? I think it does. His argument for the essence of reality as extension may survive via phenomenological reasoning as Descartes also uses when he ponders the piece of wax. If considered like that he may be a precursor to Kant and Husserl, no?
"The Power of Kant compels you" "The Power of Kant compels you" "The Power of Kant compels you"

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