  Two principles govern the critical temperature for superconducting
transitions: (1)~intrinsic strength of the pair coupling and (2)~effect of the
many-body environment on the efficiency of that coupling. Most discussions take
into account only the first but we argue that the properties of unconventional
superconductors are governed more often by the second, through dynamical
symmetry relating normal and superconducting states. Differentiating these
effects is essential to charting a path to the highest-temperature
superconductors.
