Recently, students of public policy making in North America have added the analysis of “political discourse” to the tools of their trade. According to the “political discourse” school, the extent to which policy ideas gain acceptability cannot always be explained rationally in terms of their logical or empirical validity, nor instrumentally in terms of the interests they serve. Often, their careers must be accounted for, at least in part, by a detailed exploration of their ideological assumptions and appeal, and their rhetorical structure and persuasiveness. Despite its many plausible and promising features, this type of analysis has, to date, rarely been performed in specific instances of policy discourse. The author presents a “political-discourse” analysis of the 1985–1988 debate over Canada's Bill C-82, “An Act Respecting the Registration of Lobbyists.” That debate brought together some of Canada's most factually informed and instrumentally motivated policy actors. Nevertheless, the participants uniformly based their arguments on broad assumptions unsubstantiated by empirical analysis, and advanced those arguments in the rhetoric of the public good and democratic theory. The author concludes that underlying the two basic positions taken in debate over C-82—support for a regime of substantial disclosure of lobbying activity on the one hand, and opposition to disclosure on the other—were two competing sets of assumptions concerning the nature and workings of the faculties of reason and perception in politics.