A broad assumption in argumentation theory is that argumentation primarily regards resolving, confronting, or managing disagreement. This assumption is so fundamental that even when there does not appear to be any real disagreement, the disagreement is suggested to be present at some other level. Some have questioned this assumption (most prominently, Perelman and Olbrechts-Tyteca, and Doury), but most are reluctant to give up on the key idea that persuasion, the core of argumentation theory, can only regard disagreements. We argue here (...) that this assumption is false. Argument may be as much about strengthening or maintaining agreement as it is about disagreement. Once we see how argument is possible and manifestly enacted under conditions of agreement, then we have tools to explain otherwise curious fallacies and argumentative phenomena. (shrink)