The purpose of this talk is to show, in a simple way, how the Seiberg-
Witten superpotential for N = 2 supersymmetry can be obtained by using
symmetry principles. In fact, the superpotential is determined by a c
ombination of supersymmetry, SU(2) gauge invariance, and the subgroups
of SL(2, Z) associated with Fuchsian functions. Electromagnetic duali
ty is obtained as a consequence rather than an input.