Theory Aspects of Double-Spin Asymmetries in Proton-Nucleon Collisions

The study of two spin asymmetries in hadron-hadron collisions probes the details of fundamental particle interactions in ways infeasible to machines with unpolarized collisions. Within reach is how the proton spin is distributed among its constituents through $\Delta G$ and $\Delta\bar{q}$. Measuring couplings, furthering our understanding jet structure and uncovering new physics are all among the possibilities available at polarized colliders. Spin physics may also deepen our understanding of higher twist behavior and the transition between perturbative and nonperturbative physics. An overview of the double spin physics is presented in this report. (Talk presented during the Workshop on the ``Prospects of Spin Physics at HERA'' held at DESY-Zeuthen, Germany, 28-31 August 1995.)