In this chapter I discuss some interesting historical cases in which Ockham's razor has been put to use, but the main focus is on the history of attempts to justify the principle of parsimony. Why buy the idea that simpler theories are better than theories that are more complex? A variety of answers to this question have been offered. Some think that the principle of parsimony is justified by what we have learned from observing nature. Others think that the razor has a theological justification. Still others think that valuing parsimonious theories is part of what it means to be rational. And yet another faction regards the principle as rock bottom – they think the principle is correct but that it can't be justified at all.

The snapshots I present in this chapter are varied, but there is agreement on something important – that parsimony is not an optional, aesthetic frill. Was this historical consensus on the right track? In this chapter, I use this history to begin assembling epistemological tools for assessing the status of parsimony considerations; the search for tools will continue in subsequent chapters.

The naming ceremony

It may seem that the inevitable start of our story is William of Ockham (c. 1285–1348), since it is he for whom the principle was named. The naming ceremony apparently occurred long after Ockham. In his 1649 book On Christian Philosophy of the Soul, Libert Froidmont (1587–1653) claims to coin the phrase. He speaks of a “novacula occami” (a novacula is a small knife or razor) in describing one of Ockham's critics, Gregory of Rimini (d. 1358), who

It is pleasing that this name for the principle comes to us from someone whose name means cold mountain. Quine (1953a, p. 4) says that the principle of parsimony expresses a “taste for desert landscapes,” but he could just as easily have said that the principle evokes the austere beauty of a frozen summit.