“To me it seems that those sciences are vain and full of error which are not born of experience, mother of all certainty, first-hand experience which in its origins, or means, or end has passed through one of the five senses. And if we doubt the certainty of everything which passes through the senses, how much more ought we to doubt things contrary to these senses – ribelli ad essi sensi – such as the existence of God or of the soul or similar things over which there is always dispute and contention. And in fact it happens that whenever reason is wanting men to cry out against one another, which does not happen with certainties. For this reason we shall say that where the cry of controversy is heard, there is no true science, because the truth has one single end and when this is published, argument is destroyed for ever.”

“We must doubt the certainty of everything which passes through the senses, but how much more ought we to doubt things contrary to the senses, such as the existence of God and the soul.”

“If a man will begin with certainties, he shall end in doubts; but if he will be content to begin with doubts, he shall end in certainties.”

“For this reason, the question whether miracles occur can never be answered simply by experience. Every event which might claim to be a miracle is, in the last resort, something presented to our senses, something seen, heard, touched, smelled or tasted. And our senses are not infallible. If anything extraordinary seems to have happened, we can always say that we have been the victims of an illusion. If we hold a philosophy which excludes the supernatural, this is what we always shall say. What we learn from experience depends on the kind of philosophy we bring to experience. It is therefore useless to appeal to experience before we have settled, as well as we can, the philosophical question.”

“If in other sciences we should arrive at certainty without doubt and truth without error, it behooves us to place the foundations of knowledge in mathematics...”

“Really, doesn´t everything make sense? There are, of course, things from which we more or less recover, although some of them are too harsh even for saints. But that is no reason to accuse God. Even if there are reasons to doubt him, the fact that he did not arrange the world like a well-ordered parlor is not one of them. It speaks rather in his favor. This used to be much better understood.”