Named for the Medeaval philosopher/theologian William of Ockham (c. 1285-1349), Ockham's razor is a logical principle used to eliminate competing explanations. This principle maintains that when we are faced with two competing explanatory theories each with equal explainitory power, always choose the simpler of the two theories. For example take the Ptolemaic verses Newtonian explanation of celestial motion. Both theories give an account of the phenomena we encounter (i.e., the motion of the planets, stars, etc.). Ockham's razor tells us to take the simpler of the two theories, in this case the Newtonian model. Inherent in Ockham's razor is the belief that simplicity more closely approximates the truth than complexity.