Abstract.The basic laws of physics for particles and fields can be formulated in terms of variational principles. The initial development of a variational principle had distinct teleological implications. The formulation of physical laws in terms of variational principles is outlined with specific reference to classical and quantum mechanics and field theory. Because of time irreversibility no variational principle exists for thermodynamics. In order to obtain time irreversibility molecular trajectories must be abandoned in the lowest‐level description of complex multicomponent systems. A (...) more open set of possibilities results. I suggest that this may be more consistent with a modern teleology. (shrink)