Sprung pipes up:
Momentous events may ultimately settle arguments, for instance by discrediting Hooverian retrenchment in the face of Depression. Successful politicians articulate what's not working, and why -- though sometimes, for sure, cleverly packaged nostrums win the day, short-term. "The gravitational pull of mounting social change" is shaped gradually by event and argument - as in the spectacle of Martin Luther King's peaceful demonstrators being beaten and having debris heaped on them -- and also eventually captured by effective argument, as in the California court these recent weeks on gay marriage (Judge: whom does it hurt, and how? No answer...).