From the Foundation series (1951):
Violence … is the last refuge of the incompetent.
There’s a great essay forum over at Mobilizing Ideas reviewing and discussing research on why social movements fail. It features some of my favorite researchers on this topic and is likely to be interesting to many readers of this blog. Check it out here (h/t to the ever-awesome Jay Ulfelder for pointing it out). My personal favorite is Kevan Harris’ article on the 2009 Green Movement, which critiques the view that the movement failed primarily because of state repression.
A few other reads that include analyses of why nonviolent campaigns succeed as well as why they fail: