We need normative criteria for public debate behaviour, in the form of a heightened awareness in the public sphere and in the media of which types of public debate behaviour are acceptable and which are not.
    A proposal for such criteria presupposes that public debate has an essential function in democracy. Increasingly, contemporary political thinkers agree that it does. Some, inspired by Habermas, think proper deliberation will lead towards consensus thanks to "the peculiarly constraint-free force of the better argument". Others, sometimes referring to the 'value pluralism' of Isaiah Berlin, to the 'burdens of judgment' according to John Rawls, or to the 'incommensurability' of values as described by Joseph Raz and others, recognize that reasonable disagreement is inevitable. But then, why would deliberation be essential to democracy?
    The answer this, recall that in the domain which Aristotle called practical reasoning, people often manage to change the views and preferences of others through arguments, even though arguments cannot compel agreement. This is so precisely because people's views taken on an issue are based on a plurality of values that are incommensurable and hence allow of reasonable disagreement - but also of argument-induced change in the priorities and interpretations of these values. To believe that individuals' preferences are predetermined, as political scientists tend to do, is a fallacy. Individuals do change their minds on political issues after hearing deliberative arguments, and when they do, they may legitimately feel they have been enlightened; so the role of deliberative debate in democracy is to help individuals to a more enlightened comparison and weighing of the pros and cons regarding the choices they face. Unlike consensus-based theories, this view assigns no compelling force to argumentation; it recognizes the inevitability of reasonable disagreement, and it does not negate or diminish the role of individual choice. That deliberative argumentation has this peculiar nature and this essential function in society was recognized by Aristotle and many later thinkers, who called it rhetoric.
    The fact that the balancing of pros and cons will often involve an essentially subjective weighing of them is a reason why the audience will need the debaters’ help and advice in this process. Public debaters presumably are individuals who have themselves found ways to compare the pros and cons, in spite of their incommensurability, and reached assessments they are confident with. Thus debaters should be helpful advisers by offering their individual assessments and the considerations that led to them, while recognizing that alternative assessments are legitimate. Precisely because there usually are legitimate, non-cancelable arguments on both sides in political debate, it is a central dialectical obligation for political debaters that they should pay proper and explicit attention to arguments supporting the opposite side.
    In contrast, I shall exemplify linguistic strategies used by contemporary politicians to try to evade their obligations, i.e., persuade citizens without offering real arguments for their own policies and without attending to arguments from the other side.