This article develops a validity inquiry heuristic from several Elder Sophists' positions on the nomos-physis controversy of the fifth and fourth century B.C.E. in Greece. The nomos-physis debate concerned the nature and existence of knowledge and virtue, and maps well to current discussion of validity inquiry in writing assessment. Beyond rearticulating validity as a reflexive, agency-constructing, rhetorical act, this article attempts to bridge disciplines by articulating validity in terms of rhetorical theory, and understanding ancient sophistic rhetorical positions as validity theory.