Man is only a subject full of error, natural and ineffaceable, without grace. Nothing shows him the truth. Everything deceives him. These two sources of truth, reason and the senses, besides being both wanting in sincerity, deceive each other in turn. The senses mislead the reason with false appearances, and receive from reason in their turn the same trickery which they apply to her; reason has her revenge. The passions of the soul trouble the senses, and make false impressions upon them. They rival each other in falsehood and deception.
– Blaise Pascal, Pensées (1670)