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Hello, My question is the following: Is there any knowledge that cannot be doubted? That is, what type of knowledge or physical event can we hold to be true with absolute certainty? Or is doubt an instrinsic part of the human condition?
Accepted:
March 2, 2007

Comments

Nicholas D. Smith
March 2, 2007 (changed March 2, 2007) Permalink

Descartes imagined that he had found something that could not be doubted in what is known as his "cogito" (a shortened form of the Latin expression "cogito ergo sum," which means "I think, therefore I am." You can see the intuitive strength of this: What would it be like to think that you were thinking, but be mistaken about that? (How could you be mistaken--because even to be mistaken, you'd have to be thinking something, right?)

Others have supposed that certain mathematical or logical truths are also indubitable (such as 2+2=4, or "if p then p"). But even Descartes thought that mathematical and logical truths are dubitable in some sense--even if we can't imagine what it would be like for them to be false, Descartes argued that we can imagine being so badly deceived (by an immensely powerful evil demon, say) that it could be that something we couldn't imagine being false might still actually be false.

And some philosophers have also said that we can provide some reason for doubting even Descartes' cogito, on somewat similar grounds. Why couldn't the immensely powerful demon not so confuse us that we would not be able to discriminate between the experiences of thinking and (say) feeling an itch? If we could not make the appropriate discriminations by which we can tell that a given case of thinking really is thinking, then we might be mistaken even about this.

But even if such considerations show that there can always be some room for doubt, I think that actually doubting such things is in some very deep way impractible. So perhaps this fact is just as important as the fact--if it is a fact--of their dubitability in principle.

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