Effective Charges in Non-Abelian Gauge Theories

The question of the definition of effective charges for non-abelian gauge theories is discussed, focusing in particular on both the pinch technique and background field method approaches. It is argued that there does exist a unique generalization of the QED concept of an effective charge to non-abelian theories, and that this generalization is given by the pinch technique. The discussion is set in the wider (and controversial) context of the definition of gauge-independent Green function-like quantities in general in such theories.