While there is much discussion of the need for democracy in transnational institutions, there is less discussion of the conditions for their democratisation. To address this deficit, a general account of democratisation is necessary. I propose that democratisation is dependent on the joint realisation of two conditions: communicative freedom and communicative power. Democratisation thus requires, first, publics and associations in which communicative freedom is realised on the one hand; and, second, institutions that link such freedom to the exercise of communicative power to decision making on the other. In order for these conditions to be met, civil society must be expanded into the public sphere. The transformation of communicative freedom into communicative power can be promoted only by institutions that recognise the decisional status of publics, which in turn depend on civil society to generate the deliberative benefits of the plurality of perspectives. Communicative power is not merely spontaneously generated through publics, but also through publics expressly formed through democratic institutional design.