Sources of Knowledge — Rationalism versus Empiricism

Where does knowledge come from? Two great traditions in early modern philosophy give opposing answers. Rationalism holds that reason is a fundamental source of substantive knowledge about the world, and that some ideas or truths are available independently of sensory experience. Empiricism holds that all our concepts and all our substantive knowledge ultimately derive from experience. The dispute is not about whether we use our senses and our reason, since everyone agrees we use both, but about which faculty is the ultimate foundation and whether the mind contributes anything of its own prior to experience.

A priori and a posteriori

A useful distinction organizes the debate. A proposition is known a priori if it can be justified independently of experience, by thought alone; "all bachelors