  What is sometimes called the "totalitarian principle," a metaphysical
doctrine often associated with the famous physicist Murray Gell-Mann, states
that everything allowed by the laws of nature must actually exist. The
principle is closely related to the much older "principle of plenitude."
Although versions of the totalitarian principle are well known to physicists
and often appear in the physics literature, it has attracted little reflection.
Apart from a critical examination of the origin and history of the totalitarian
principle, the paper discusses this and the roughly similar plenitude principle
from a conceptual perspective. In addition it offers historical analyses of a
few case studies from modern physics in which reasoning based on the
totalitarian principle can be identified. The cases include the prediction of
the magnetic monopole, the hypothesis of radioactive protons, and the discovery
of the muon neutrino. Moreover, attention is called to the new study of
metamaterials.
