Ockham's Razor / Occam's Razor / Principle of Simplicity

Ockham's Razor

Biography

William of Ockham (also spelled Occam) was living in the Middle Ages (ca. 1285 – 1349). He was born in England in a town called Ockham near Ripley, Surrey. William devoted to a life in extreme poverty and minimalism and lived as a Franciscan friar and philosopher. He became a pioneer of nominalism, the position in metaphysics, that there exist no “universals” outside of the mind. Besides he was theologian, an outstanding logician and concentrated on epistemology and modern philosophy in general.

In 1324 he was suspected of heresy by Pope John XXII and spent four years under house arrest while his teaching and writing were being investigated. During this time Ockham even concluded that the Pope was a heretic. After massive dissensions between the Franciscan order and the papacy William fled to Munich and sought the protection of Emperor Louis IV of Bavaria. He spent much of the remainder of his life writing about political issues, including the relative authority and rights of the spiritual and temporal powers. He died in a convent in Munich, Bavaria, possibly as a result of the Black Death.

Definition

One of the tools Ockham used routinely in his reasoning is what is known in philosophy as the principle of parsimony, and popularly as Ockham's Razor.

Entities are not to be multiplied beyond necessity. Applied to systems of ontology or bodies of scientific theory, the principle encourages us to ask whether any proposed kind of entity is necessary. This principle of metaphysical economy retains influence in contemporary philosophy, although in judging rival systems it is not always clear which best meets the requirements of Ockham's Razor. [Bunnin and Tsui-James, 2005]

"pluralitas non est ponenda sine necessitate"; "Entities should not be multiplied unnecessarily" or "Multiplicity ought not be posited without necessity". The principle that if two theories explain a phenomenon equally, the simpler theory requiring fewer assumptions and explanatory principles is preferred and that generalizations should be based on observed facts and not on other generalizations. One hallmark of pseudoscience is the requirement for many assumptions and untestable explanatory principles to support the core theories, which proponents often change when an assumption or principle is critically refuted. Under this principle, the theory containing testable components is preferred over the theory containing an inherently untestable component. [John Gay, 2005]

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Rules/Conclusion

Rules

Just as for the Golden Rule, there are many ways of stating Ockham's Razor. Here are four that William of Ockham used in his works:[Hoffmann et al., 1997]

• It is futile to do with more what can be done with fewer. [Frustra fit per plura quod potest fieri per pauciora.]
• When a proposition comes out true for things, if two things suffice for its truth, it is superfluous to assume a third. [Quando propositio verificatur pro rebus, si duae res sufficiunt ad eius veritatem, superfluum est ponere tertiam.]
• Plurality should not be assumed without necessity. [Pluralitas non est ponenda sine necessitate.]
• No plurality should be assumed unless it can be proved (a) by reason, or (b) by experience, or (c) by some infallible authority. [Nulla pluralitas est ponenda nisi per rationem vel experientiam vel auctoritatem illius, qui non potest falli nec errare, potest convinci.]