"There are four chief obstacles to grasping truth: authority, habit, popular opinion, and the concealment of ignorance."

"It is better to learn from the infidels than to remain in ignorance."

"The four greatest stumbling blocks to understanding are: authority, long-standing custom, the sense of the ignorant crowd, and the hiding of one's own ignorance under the show of wisdom."

"He who knows not mathematics cannot know any other sciences."

"There are many fables and falsehoods in the books of the Latins, which are taken for truths."