Totalitarian principle
In quantum mechanics, the totalitarian principle states: "Everything not forbidden is compulsory." Physicists including Murray Gell-Mann borrowed this expression, and its satirical reference to totalitarianism, from the popular culture of the early twentieth century. The statement refers to a surprising feature of particle interactions: that any interaction that is not forbidden by a small number of simple conservation laws is not only allowed, but must be included in the sum over all "paths" that contribute to the outcome of the interaction.