Deliberation has not only epistemic and moral value, it also has transformative value. Even if deliberation faces the problem of indeterminacy, it is assumed to have explanatory power. This article spells out why this is so and suggests a way to establish the causing effect of deliberation. It outlines a reason-based (RB) model of political decision-making applicable also to international affairs. By specifying a theory of argumentation on collective decision-making, we get to the nuts and bolts of deliberative decision-making, which, when supported by institutional powers, ensures a justified and well-grounded decision. The model contains a set of rules of inference and offers ‘mechanismic’ accounts of social events. It allows for explanations, but not predictions. The RB model conceives of decision-making as consisting of three sequences: claims-making, justification, and learning, each containing a set of explanatory mechanisms: values referring to conceptions of the common good, mandatory norms concerning the right thing to do, and evidence to the fact that non-compliance is wrong. The explanatory potential of this scheme is exemplified with reference to agreement making in the European Union. Some actors changed opinion voluntarily with regard to empowering the European parliament.
Getting to agreement: mechanisms of deliberative decision-making