What Augustine means is that the fundamental touchstone for validity in interpreting Scripture is the rule of charity, the love of God and of our neighbor. Any interpretation that conforms to this rule is valid even though it may be incorrect...While Augustine recognizes the Rule of faith as a necessary criterion for valid interpretation, he insists that the only sufficient criterion is the rule of charity. The close connection between right belief, right understanding, and right living is obvious.
On some level, I agree with Augustine here: when the meaning of Scripture is ambiguous, go with the interpretation that promotes love. Let's take my post yesterday as a case in point: Ambiguities in II Samuel 14. Does the author of II Samuel 14 believe that David was right or wrong to pardon Absalom? It's not clear, as far as I can see. But the text still can teach me lessons about reconciling with people before it's too late.
The problem arises when I have to make really tough decisions. Suppose I were on a jury, and I had to decide whether or not a person would get the death penalty. Would I go with justice and vote to execute him? Would I vote with love and mercy, recognize the defendant's humanity, and give him another chance to make a life for himself? Or would refusal to apply the death penalty be unloving towards society, especially the victims? Ironically, Augustine himself supported the death penalty, even though some use his "charity criterion" to support a "canon within a canon" (City of God 1:21).
People have tried to come up with iron-clad rules on what to do. Martin Luther said we should reconcile with people on a private, individual level, but our duty as magistrates is to execute justice, even if that involves the death penalty. The problem is that the lines get pretty blurred in II Samuel 14. David is a magistrate, yet he refuses to execute his murderer son because he wants to imitate God and be merciful. Can mercy ever require us to set aside the rules, to treat God's law as less than iron-clad?
There are many liberal theologians who think we should do precisely this. They look at the Bible and see things that aren't all that loving: genocide, slavery, subordination of women, the death penalty for homosexuals. Some may reinterpret the Bible to fit their idea of love. Others say we should set aside the non-loving parts of Scripture and go with the loving parts.
Then there's the question of what "love" is. Is it love for Christian churches to say that homosexuals can't have a lifelong sexual relationship with someone of the same sex? Some consider that to be cruel. Others say conservative Christians actually love homosexuals when they preach against homosexuality, since the homosexual lifestyle can lead to STDs, unhappiness, and (ultimately) hell-fire. And liberals can come back and say that homosexuals are unhappy because society doesn't accept them, which isn't very loving.