Man is nothing but a subject full of natural error that cannot be eradicated except through grace. Nothing shows him the truth, everything deceives him.
The two principles of truth - reason and senses - are not only both not genuine, but are engaged in mutual deception.
The senses deceive reason through false appearances, and, just as they trick the soul, they are tricked by it in return: it takes its revenge. The senses are disturbed by passions, which produce false impressions.
They both compete in lies and deception.
Blaise Pascal - Pensees - Number 45. Translated by AJ Krailsheimer, Penguin edition of 1966.
Since, as Pascal shows, we have no reason to believe either reason or the evidence of the senses (experience), whence comes truth?
Only by grace - in other words from God.
Truth is either inbuilt by God (in the form of inborn reason) and/ or truth is received by revelation from God during the human lifespan derived from the evidence of our senses - by experience, as an increase in genuine knowledge.
Reject God and you reject both reason and the evidence of the senses as sources of genuine knowledge.
(Neither chance nor evolution could arrange matters such that reason and/or the senses provided genuine knowledge; why should they?)
The choice is God or nihilism (denial of truth, of reality): there is no other option.