Brooks meditates on it here. I was thinking about the difference between instincts and judgment the other day with regard to Iraq. One reason McCain got the conduct of the Iraq war right while Bush got it wrong for too long was that McCain had more experience in these matters. So while Bush had instincts (most of which McCain shared), McCain had judgment. He could independently evaluate what he was hearing from the military, knew what questions to ask, and could apply historical examples to current circumstances. It made a huge difference.