[From the introduction]. Arguing, understood as reason-giving, is all pervasive in international politics: Negotiating actors give reasons for their demands at almost any time, regardless of whether talks are con-ducted in public or behind closed doors. And yet, since negotiations have most often been conceived of as processes of bargaining in which actors seek to adjust their behavior through the exchange of threats and incentives, arguments have primarily been treated as rather epiphenomenal to strategic interaction. In this paper we argue that under certain circum-stances arguments affect negotiating actors’ preferences, and subsequently lead to outcomes that are not easily explained in pure bargaining terms. Arguing and bargaining as different modes of interaction, however, are not contending but rather complementing explanations. As a result, we have to ask which scope conditions are particularly conducive to enabling arguing to prevail in decentralized negotiations and, thus, to affect both process and outcome. In a structured-focused comparison of Intergovernmental Conferences (IGCs) with the European Convention we aim to unveil institutional factors that induce actors to take validity claims into account and change their preferences accordingly. At the example of negotiations on sim-plification and the single legal personality of the European Union we seek to demonstrate that the transparency of the debate in conjunction with a higher degree of uncertainty about appro-priate behavior made arguing in the Convention particularly effective
