To me it seems that those sciences are vain and full of error which are not born of experience, mother of all certainty, firsthand 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 such as the existence of god or of the soul or similar things over which there is always dispute and contention.