This essay considers the role of the ‘all affected interests’ principle in democratic theory, focusing on debates concerning its form, substance and relationship to the resolution of the democratic boundary problem. It begins by defending an ‘all actually affected’ formulation of the principle against Goodin’s ‘incoherence argument’ critique of this formulation, before addressing issues concerning how to specify the choice set appropriate to the principle. Turning to the substance of the principle, the argument rejects Nozick’s dismissal of its intuitive appeal (...) and considers the two arguments advanced in favour of the principle as a criterion of democratic inclusion: the interlinked interests argument and the tracking power argument. It is shown that neither of these arguments can substantiate a view of the principle as a criterion of democratic inclusion, although both ground a constitutional understanding of the principle as specifying the scope of a duty of justification. It is then proposed that the principle can play an important role in a two-stage resolution of the democratic boundary problem in which it addresses the question of who is entitled to inclusion in the ‘pre-political’ demos that determines whether to constitute a polity. The second stage of this resolution requires an answer to the question of who should constitute the ‘political demos’, that is, the demos of a constituted polity and it is argued that a version of the ‘‘all subjected persons’’ principle can appropriately play this role.Keywords: all affected interests; all subjected persons; democracy; boundary problem; demos problem. (shrink)