The Context of High Energy QCD Spin Physics

Opening talk presented at the Adriatico Research Conference -- Trends in Collider Spin Physics and at the RIKEN Symposium -- Spin Structure of the Nucleon. We present an overview of the opportunities to explore QCD at a very high energy polarized hadron collider. We review connections to low energy flavor physics, transverse spin in QCD and higher twist. It is clear that polarized colliders will provide a wealth of new information about the behavior of quarks and gluons inside hadrons complementing that available from lepton scattering and other more familiar probes of hadron structure.