In November 1938 Columbia Theological Seminary published an interview with Karl Barth. It's not the most enlightening interview you'll ever read. Most of the questions (asked by William Childs Robinson) take the form: "Is it true that...?" or "Given what you have said, does this mean that...?" For this reason Barth's responses rarely rise above the level of "Yes," or "No," or "I wouldn't quite put it that way." Indeed, as you read the interview you realise just why you had never discovered what 5 minutes ago appeared to be a hidden gem. The interview is little more than a wasted opportunity, really, but then we hardly lack for words by or about Karl Barth.
Still, there is one question and answer that gives a good summary of what Barth is up to in his theology. William Robinson asks:
"Would you describe sin as the transgression of the law of God?" (what did I tell you?)
You might expect Barth to respond with a simple "Yes," but he has something a little difference up his sleeve. He replies:
"Not primarily. Sin is first a protest against grace. There is no law apart from grace. Of course, grace gives a law, but what makes sin condemnable is our resistance against His love, not against His commandments. The Gospel comes before the law and love before the claim."
With these few sentences the traditional configuration of law -> sin -> grace is criticised and re-configured. For Barth, the true order is grace -> sin -> grace -> law (or perhaps grace -> law -> sin). This is why Barth says elsewhere the only Christians can properly sin, since Christians are the ones who know the grace (and the God) against which they sin. Indeed, our chief sin is our attempt to understand sin apart from grace. Barth's name for this attempt is "ethics."
One thing worth thinking about is what Barth's order would do to the practice and content of evangelism.