This essay explores the way Angelo and Isabella appeal to rules in their attempts to justify the legality or ethics of their actions, and thus relieve themselves of the burden of responsibility. ("It is the law, not I, condemn your brother.") However, the play will confront them with the truth that all rules, even the most precise, require a human agent to use them in a particular context. ("O, it is excellent / To have a giant's strength, but it is tyrannous / To use it like a giant.") No rule is so determining that it can determine its own uses. However, for Angelo and Isabella to justify their uses, which cannot be done by appealing again to the rule, not only burdens them with responsibility but also makes their actions seem arbitrary—potentially resting on nothing more than personal inclination. I therefore characterize the drama of Measure for Measure as an oscillation between the authority of the rules with which human agency is stamped, and a recognition of the contingent human agent that bears the stamp. I argue that this drama has similarities with Ludwig Wittgenstein's characterization of our problematic understanding of any rule-governed activity, including language: we aspire to justify our practices with rules that have the precision and objectivity of a mathematical calculus, but we are inevitably thrown back upon our own uses, which seem comparatively unruly and imprecise.