But it is not yet proved by adamant being broken by blood of this kind, as much as it is argued to this conclusion. And yet, even without the blood it can be broken with ease. Similarly it is commonly believed that the secretions of the beaver that the doctors use are the testicles of the male, but this is not so, as the beaver has this secretion beneath its breast and even the male as well as the female produces a secretion of this kind. In addition also to this secretion the male has its testicles in the natural place and thus again it is a horrible lie that, since hunters chase the beaver for this secretion, the beaver knowing what they are after, tears out his testicles with his teeth and throws them away. It is necessary, then, to prove everything by experience.
Experience is of two kinds.
And facts that are not true in places where we are, we know through other wise men that have experienced them. Thus Aristotle with the authority of Alexander, sent 2,000 men throughout various parts of the earth in order to learn at first hand everything on the surface of the world, as Pliny says in his Natural History. And this experience is human and philosophical just as far as a man is able to make use of the beneficent grace given to him, but such experience is not enough for man, because it does not give full certainty as regards corporeal things because of their complexity and touches the spiritual not at all. Hence man's intellect must be aided in another way, and thus the patriarchs and prophets who first gave science to the world secured inner light and did not rest entirely on the senses. So also many of the faithful since Christ.