The Philosophical Writings of Descartes

A good man is not required to have read every book or diligently mastered everything taught in the Schools. It would, indeed, be a kind of defect in his education if he had spent too much time on book-learning. Having many other things to do in the course of his life, he must judiciously measure out his time so as to reserve the better part of it for performing good actions – the actions which his own reason would have to teach him if he learned everything from it alone. But he came into the world in ignorance, and since the knowledge which he had as a child was based solely on the weak foundation of the senses and the authority of his teachers, it was virtually inevitable that his imagination should be filled with innumerable false thoughts before reason could guide his conduct. So later on he needs to have very great natural talent, or else the instruction of a wise teacher, in order to rid himself of the bad doctrines that have filled his mind, to lay the foundations for a solid science, and to discover all the ways in which he can raise his knowledge to the highest level that it can possibly attain.