William of Ockham
He is commonly known for Ockham's razor, the methodological principle that bears his name, though it may be a much older idea. "Entities are not to be multiplied without necessity" (Non sunt multiplicanda entia sine necessitate) was said to be implied by the works of Duns Scotus as well as earlier thinkers. For example, Aristotle had written in his Posterior Analytics, "We may assume the superiority ceteris paribus (other things being equal) of the demonstration which derives from fewer postulates or hypotheses." This is sometimes called the "law of parsimony."