Polarization asymmetries and gauge theory interactions at short distances

In this talk, which summarizes the theoretical considerations behind talks given in the plenary sessions of the SPS workshop on the role polarization measurements can play at high energies, we give the arguments as to why spin asymmetries test fundamental properties of the underlying gauge theories of elementary particles, concentrating mainly on electro-weak and QCD interactions, but also looking to the future and possible signatures for supersymmetric strong interactions. We also mention briefly the role helicity asymmetry measurements can play as regards higher order corrections, including higher twist, in QCD. (author)