"Physics, Astronomy, Medicine, and all the other sciences that have for their end the consideration of composite objects, are indeed of a doubtful character; but Arithmetic, Geometry, and the other sciences of the same class… contain somewhat that is certain and indubitable: for whether I am awake or dreaming, it remains true that two and three make five, and that a square has but four sides; nor does it seem possible that truths so apparent can ever fall under a suspicion of falsity [or incertitude].’ (2) Do you agree that there are some things that simply will always be true (or false)?"
I see what Descartes is saying here. Anything that relies on something outside of ourselves is subject to the infallibility of our senses. Things like Arithmetic, Geometry, and -”hey!”- even Philosophy... These don’t need to necessarily exist anywhere but in our thoughts. If you start to think about the makeup of mathematics, and some of these sciences, you realize they don’t really exist anywhere except in the minds of men. Something I find profoundly interesting. These sciences are difficult to argue with since you know your own thoughts exist, and numbers (any system of reasoning) seem logical to any “rational person”. I would have to ask Descartes, at this point however, how well he could trust his logical mind. Ultimately, I disagree that there are some things that will always be true. It is possible to use logic in such a way that it "undoes" itself. You can bring doubt to what are seemingly apparent truths by undermining the mental process used to arrive at whatever conclusions. If you can successfully do that, then one would have to assert even sciences which seem so apparent may indeed be another deception.
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You raise an excellent point, Gavin, albeit one that is hard (which is not to say impossible) to explore further: why should we trust logic? The thing is, we have as much reason to trust logic as we do anything, but why can't we doubt even this?
ReplyDeleteThe problem -- for Descartes, perhaps, but also for the skeptic that proclaims the fallibility of logic -- is: how can he then argue that logic is infallible, since argument uses logic?
However, I wouldn't say it's so easy to generalize that 'It is possible to use logic in such a way that it "undoes" itself' -- not, at least, without providing specific evidence.