Mental Floss

5 Rules of Thumb and Their Inventors

Casey Johnston

It is a popular custom among learned society to toss around the names of theories without explanation or elaboration-- Murphy's Law, Occam's Razor, and so on. But who were Murphy and Occam, and who are they to come up with these life-governing rules? Below are five well-known rules and laws, and the stories behind their namesakes.

1. Occam's Razor

Occam's razor is known more formally as the law of parsimony or the law of economy, and states that "entities should not be multiplied unneccesarily." Put simply, it is the notion that the simplest explanation is usually the right one. It is named after William of Occam, who was a scholastic philosopher and Franciscan friar that lived in England in the 14th century. His contemporaries were the likes of Thomas Aquinas and the Islamic scholar Averroes. William was the first to write down the principle in its formal wording, and it gained his name due to its frequent usage in medieval philosophy. William was also one of the first to argue that people should not attempt to derive the idea of God from reason or natural logic.

2. Moore's Law

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3. Murphy's Law

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4. Pareto Principle

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5. Parkinson's Law

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