Gyaan Sutra

However clear and distinct our ideas might be, we should have no ground on that account for the assurance that they possessed the perfection of being true.

But after the knowledge of the god and the soul has rendered us certain of this rule, we can easily understand that the truth of thoughts we experience when awake, ought not in the slightest degree to be called in question on account of the illusions of our dreams. For if it happened that an individual, even when asleep, had some very distinct idea, the circumstance of his being asleep would not militate against its truth; and as for the most ordinary error of our dreams which consists in their representing to us various objects in the same way as our external senses, this is not prejudicial, since it leads us very properly to the truth of the ideas of sense; for we are not infrequently deceived in the same manner when awake.

For infine, when awake or asleep, we ought never to allow ourselves to be persuaded of the truth of anything unless on the evidence of our reason.

- Rene Descartes