A reactor scale tokamak plasma will exhibit three areas of physicsphenomenology not accessible by contemporary experimental facilities. These are: (1)instabilities generated by energetic alpha particles; (2) self-heating phenomena; and(3) reactor scale physics, which includes integration of diverse physics phenomena,each with its own scaling properties. In each area, selected examples are presentedthat demonstrate the importance and uniqueness of physics results from reactor scalefacilities for both inductive and steady state reactor options. It is concluded thatthe physics learned in such investigations will be original physics not attainablewith contemporary facilities. In principle, a reactor scale facility could have a goodmeasure of flexibility to optimize the tokamak approach to magnetic fusion energy.