Joint group decisions are very often achieved via a decision rule that is usually neglected in theory, though familiar to all of us from social settings and committee experiences: decision-making by ‘tacit consent’, i.e. by the absence of any open opposition. Widely known examples of its application in ‘High Politics’ are the Council of the European Union, the European Council or the World Trade Organisation, where decisions are made ‘consensually’, while voting is avoided.
Building on theories of decision-making, deliberation, conversation and institutionalism and with reference to empirical cases from various different settings in international and domestic politics, the paper depicts the constitutive mechanism of this decision rule and spells out the mode’s institutional, though usually informal nature as well as its enforcement via social norms. On these grounds the democratic quality of the decision mode is discussed. It is argued that consensual decisions taken by tacit consent differ substantially from unanimous votes and that, contrary to conventional wisdom, the veto option in these procedures is in fact in many ways constricted and very often de facto deactivated. It is shown that in normative terms, this decision rule is by no means superior to voting mechanisms, but suffers from power asymmetries and opacity, first and foremost.