Dialogue. It comes from the Greek, and covers a host of meanings from conversation, to philosophy, to speaking articulately, to lecturing, to dealing with others. It can be as contentious as it is conciliatory and as hostile as it is friendly. It can be consensus-building or polarizing, controversial or anodyne. But, at its worst and at its best, it is engagement; and, throughout its worldwide history, it has consistently done a glorious thing. It produces knowledge—or, at a minimum, it puts on display the fact that knowledge is out there.