In other words, on issue after issue, we cannot rely on a rule book written for a different century. If we lift our eyes beyond our borders -- if we think globally and if we act cooperatively -- we can shape the course of this century, as our predecessors shaped the post-World War II age. But as we look to the future, one issue risks a cycle of conflict that could derail so much progress, and that is the cancer of violent extremism that has ravaged so many parts of the Muslim world.