The state principle is an important and fundamental thermodynamic concept. Having only recently been formally stated however, there is still some disagreement as to the basis of the principle＇s derivation. An examination of various state principle presentations leans to the conclusion that the state principle must be based on the first and second laws, and, additionally, that the energy, the amounts of the constituents, and the parameters solely determine property. Microscopic properties and nonequilibrium states are not inherently governed by the state principle, but extensions have been formulated to incorporate these areas.