While doing research, I ran accross Ockham's Razor - the Law of Succinctness (lex parsimoniae) - which is frequently attributed to William of Ockham. In english, the statement he made translates to:
entities should not be multiplied beyond necessity
The legend/myth comes along after his death with other philosophers applying this law and refering to it as Ockham's Razor. The manner in which they use it is such that with all things equal, the simplest explination is the correct explination.
I prefer quoting Fox Mulder on the X-Files and calling it: Ockham's Principle of Unimaginative Thinking