“Rhetoric includes “performative” uses of language that make a difference in one’s relation to the object of study. This does not mean that the historian is obliged to resort to explicit moral judgments, overt didacticism in drawing lessons, or “show and tell” sessions in which one’s values or autobiographical propensities are bared to one’s audience. The more direct forms of public exposure generally serve a purgative function and rarely inform an account in a telling or transformative way.”