At once two things came to mind: fear and desire: fear of the threatening dark cave, desire to see if there was anything miraculous within it.(referr… - Leonardo da Vinci

If you find from your own experience that something is a fact and it contradicts what some authority has written down, then you must abandon the authority and base your reasoning on your own findings.

Creatures shall be seen on the earth who will always be fighting one another, with the greatest losses and frequent deaths on either side. There will be no bounds to their malice; by their strong limbs the vast forests of the world shall be laid low; and when they are filled with food they shall gratify their desires by dealing out death, affliction, labour, terror, and banishment to every living thing; and then from their boundless pride they will desire to rise towards heaven, but the excessive weight of their limbs will hold them down. Nothing shall remain on the earth or under the earth or in the waters that shall not be pursued, disturbed, or spoiled, and that which is in one country removed into another. And their bodies shall be made the tomb and the means of transit of all the living bodies they have slain.
O earth, why do you not open and hurl them into the deep fissures of thy vast abysses and caverns, and no longer display in the sight of heaven so cruel and horrible a monster?

There will be many who will eagerly and with great care and solicitude follow up a thing, which, if they only knew its malignity, would always terrify them. Of those men, who, the older they grow, the more avaricious they become, whereas, having but little time to stay, they should become more liberal.