It is possible that I am dreaming right now and that all of my perceptions are false.

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I am indeed amazed when I consider how weak my mind is and how prone to error.

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At last I will devote myself sincerely and without reservation to the general demolition of my opinions.

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It is not enough to have a good mind. The main thing is to use it well.

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De omnibus dubitandum.
Doubt everything.

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If you would be a real seeker after truth, it is necessary that at least once in your life you doubt, as far as possible, all things.

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Nothing comes out of nothing.

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The first precept was never to accept a thing as true until I knew it as such without a single doubt.

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I can doubt everything, except one thing, and that is the very fact that I doubt. Simply put – I think, therefore I am.

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Let whoever can do so deceive me, he will never bring it about that I am nothing, so long as I continue to think I am something.

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I find not a single property which with certainty separates the waking state from the dream.

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Everything is self-evident.