Barrier to Catholic-Orthodox unity

It depends on what "unity" means, says Frederica Mathewes-Green, and she's exactly right:

But from an Orthodox perspective, unity is created by believing the same things. It's like the unity among vegetarians or Red Sox fans. You don't need a big bureaucracy to keep them faithful. Across wildly diverse cultures, Orthodox Christians show remarkable unity in their faith. (Of course there are plenty of power struggles and plain old sin, but the essential faith isn't challenged.) What's the source of this common faith? The consensus of the early church, which the Orthodox stubbornly keep following. That consensus was forged with many a bang and dent, but for the past millennium major questions of faith and morals have been pretty much at rest in the Eastern hemisphere.