I was reading Descartes first meditation for a philosophy class and I agree most of what he says. For example the stuff about how we can’t be certain about our senses and cant base all our knowledge off of it. But I don’t agree with some of the “evil Genius” stuff.
He wants us to imagine a situation where there is an evil genius that has tricked us into every thing we know. What we belive to be true is actually false.
Descartes says:
And I can agree with all that. Our senses could be decived in that way. But what I dont agree with is when he says:
How could an evil genius, no matter how powerful, convince us that 2+3=4 or that a triangle actually has 5 sides? Arent these things self evident? Thier existances is purley conceptual and would cease to exist if they changed. For example a triangle having five sides isnt a triangle.
How could an evil genius, no matter how powerful, convince us that 2+3=4 or that a triangle actually has 5 sides? Arent these things self evident? Thier existances is purley conceptual and would cease to exist if they changed. For example a triangle having five sides isnt a triangle.
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It doesn’t even really take an evil genius. For math in particular, all it takes are a few number theorists to change the definiton of 2+3.
Anyway, to answer your question, I’d say this: I think you are taking definitional things as “real”. The question becomes are things that are defined like a triangle actually “real”? Why couldn’t we redefine a triangle to have five sides? What keeps us from it? The previous definition? Definitions are always in flux. As mentioned in another thread, Pluto once defined as a planet, isn’t anymore.
The problem with taking a definitional thing as “real” is that it can simply be redefined as something else. Nothing stops us from doing this. Hell, it’s probably 90% of what this board is about.
my biggest problem was descartes “proof” of gods existance.
i can concieve of a perfect being so it must exist because existance is more perfect than non-existance…bla bla…who thinks he would have gave the bishop a handjob?
But it’s not somthing that is definitional it’s somthing that just is. It’s nothing like the case of pluto. Pluto is physical, its a thing. In the situation im talking about we are trying to consider that everything we know, were taught, or feel is false. We cant rely on anything. An besides pluto is the same as it always has been no matter what we call it. Just because you call an apple a bannana doesn’t make it a bannana.
Im saying that 2+3=5 and that a triangle has three sides are somthing that we allways can rely on. They are indisputable I belive. Can you concive a 5 sided triangle? How can 2+3=4? Thier statements are proof of thier truth and existance. A triangle ceases to be a triangle once it has more or less that 2 sides.
well i’m not saying that he should or should not have had faith…just that we lack evidance for or against god and we shouldn’t consider it proven like gravity or math or geometry.
i always held that their is a god(however you want to take that) regardless of the lack of evidance…so i guess i was brainwashed too…
i just think that given the attention to detail in the rest of meditations, he should have kept true to the rest of the work in his dealings with god.
actually, a triangle is a triangle exactly because we define it as such. it is exactly like pluto. but that isn’t descartes’ problem. he didn’t doubt enough. if he really wanted to doubt everything he could have. but he never did doubt everything because his belief in god wouldn’t let him before the fact…
Yeah he did. In his first meditation Descartes says:
He is doubting everything he formerly belived in order to arrive at an ultimate turth. Sure later on he reaffirms his belief in God but for the time being he is doubting everything.
Im saying that he cant doubt math. Sure we define a triangle as having three sides but it dosent have three sides because we difine it that way. We didnt invent the triangle we discovered it.
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how do we define a side? in geometry its a part of the perimeter of a plane figure. the perimiter being the overall shape of a 2-d figure. a triangle has 3 distinct line segments that intersect each other at an average of 60* and hence we say it has 3 sides.
a triangle has 3 sides, 2+4=6, anyone who knows what a side is and knows how to count can tell you that with 100% certainty.
can Descarte be 100% certain that his proof of god is equally proof for every other human that can follow along, as is the case with geometry and math? i don’t think so.
by the way, i am curious, where/when was the 1st triangle discovered? as im yet to see a straight line which was the product of natural processes, most triangles i have seen we’re in math books and most straight lines i’ve seen we’re man made(building, sidewalk, computer monitor) and im using the term straight loosely.
No…I’m pretty sure at this point he is doubting god. That’s pretty much what he said in that qoute I have. He is doubting everything, at least for right now
He says:
The key words there are nothing and all.
Math isn’t a human invention it’s a human discovery. If we didn’t exist unlike language math would not cease to exist. Two plus three would still equal five and triangles would still have three sides.
To discuss changing the definition of a triangle is simply a discussion of language, not a discussion of mathematics or geometry. Our definition of triangle is simply a word to refer to the concept of a triangle.
The idea of a triangle existing outside of human existence is to say that, even if no human or logical thinking creature existed, it would still be true that a triangle has three sides. Think of it this way, our word ‘triangle’ is taken to mean ‘a three-sided geometric figure’. So what Descartes is saying is that the evil genius cannot make him believe the following sentence to be true: “A three-sided figure has five sides.”
If we were to change the definition of triangle to be ‘a five-sided figure’ would simply change the meaning of the word ‘triangle’. It would have no effect on the objective truth that ‘a three-sided figure has three sides’.
You say that as if it’s an objective truth. I believe there are objective truths, because there are some facts, mathematical and logical facts for example, that I cannot imagine to be untrue. I believe it is an objective truth that ‘1 = 1’. I believe this to be true outside of the existence of anything. I challenge you to show me a case where this is not true.
