William of Occam (1284-1347) was an English philosopher and theologian. His work on knowledge, logic and scientific inquiry played a major role in the transition from medieval to modern thought. He based scientific knowledge on experience and self-evident truths, and on logical propositions resulting from those two sources. In his writings, Occam stressed the Aristotelian principle that entities must not be multiplied beyond what is necessary. This principle became known as Occam's Razor, a problem should be stated in its basic and simplest terms. In science, the simplest theory that fits the facts of a problem is the one that should be selected.

Excerpt from the Encyclopedia Britannica without permission.