  Political deliberation occurs when a public decision needs to be made and a proposed course of action defended. But deciding which course of action to pursue involves more than simply applying rules or calculating costs and benefits. It requires interpretation and judgment. We must decide which rule to use and then interpret what it means in a given situation. If, alternatively, we choose an action based on its likely consequences, we must judge the expected value of those consequences, and this involves making value judgments as well as estimating probabilities. Whether we are applying rules or calculating outcomes, we must work with what we presume to be facts, though these are always uncertain in various ways. For these reasons, there is never a demonstrably correct course of action. Political arguments cannot be proved or disproved; they can only be shown to be more or less convincing than other such arguments. Political discourse, then, is a discourse of contingencies and conjectures, not of certainties or context-independent truths. It is persuasive and rhetorical, not a matter of demonstration or proof (RP 70–95).