Discipline: Philosophy
Also called the principle of the best.
Principle of German philosopher and mathematician Gottfried Wilhelm Leibniz (1646-1716) that the actual world is the best of all possible worlds.
Bertrand Russell (1872-1970) argued that Leibniz did not fully distinguish this principle from that of sufficient reason.
Source:
B Russell, A Critical Exposition of the Philosophy of Leibniz (1900), §§14-15