  The most general Lagrangian for dynamical torsion theory quadratic in
curvature and torsion is considered. We impose two simple and physically
reasonable constraints on the solutions of the equations of motion: (i) there
must be solutions with zero curvature and nontrivial torsion and (ii) there
must be solutions with zero torsion and non covariantly constant curvature. The
constraints reduce the number of independent coupling constants from ten to
five. The resulting theory contains Einstein's general relativity and
Weitzenbock's absolute parallelism theory as the two sectors.
