Nonviolence hinges on a belief in the possibility of change in your 'enemy'. This belief typically comes from a trust that the truth, repeatedly and vulnerably and passionately put forth, can stir compassion in any heart (or wherever your culture metaphorically places compassion in the body). Given the human brutality in known history, this seems hopelessly naive to many, but history is also full of evidence for it's truth, especially in the last century:
Wink also points to Jesus Christ as an early nonviolence strategist. Many of his teachings on nonviolence become far more sophisticated when one knows their context. For example, among the people he was speaking to, if by collecting debts you drove someone to be naked, great shame fell on you, not the naked man. So Jesus' suggestion -- that if someone ask you for your coat you give him your clothes as well -- is a way for someone to make a powerful point to the person who's indebted them to ruin.
This kind of creativity is typical of nonviolent movements, because something unusual is needed to get people's attention on violence they have become accustomed to. Aristophanes' Lysistrata gives the fictional example of women withholding night time fun to their husbands until the war was abandoned. Gene Sharp wrote a widely known list of 198 Nonviolent Strategies in 1973, which includes symbolic, political, economic and physical actions.
Ruinous debt is also one example of the violence inherent in most social systems, which in addition to its direct consequences, makes other kinds of violence possible and likely:
Practicing nonviolence ultimately goes deeper than withholding from violent behavior or words, to caring in one's heart for everyone, even those one strongly disagrees with. An often-missed implication is that this includes having care toward those who are not practicing nonviolence. Of course no one can simply will themselves to have such care, and this is one of the leading edges of nonviolence today -- once one believes in nonviolence in theory, how to live it? Most societies & cultures could support nonviolence a great deal more than they do, so the struggle is both individual and collective.