The postwar decades are well known for having brought dramatic change to American linguistics on many fronts. This paper explores an internally focused aspect of this change: conditions of explanation. The two questions at stake are, firstly, what counts as explanation in linguistics? and, secondly, how is this decided? I argue that transformational grammarians dominated the setting of explanatory criteria in 1960s American syntax, and that this dominance was essential to the overall success of that theory. Importantly, rival grammarians were forced to devote as much time and effort to fitting their theories to the transformational criteria as they were to advancing their own explanatory priorities. By successfully naming the conditions for explanation, transformationalists provided their own supporters with significant questions to pursue and, simultaneously, drew energy away from rivals. This monopoly over explanatory criteria was central to the dominant position transformational grammar established in the American academic linguistics community.