Against the easy presupposition that such a thing as 'democratic taxation' not only exists but is also practicable, this paper points to the dilemma posed by what I call 'quantifiable action.' The essay develops an approach to theorizing the place of taxation in political theory that counters trends in fiscal sociology, political science, and liberal theory by highlighting how taxation presumably violates the requirement that self-government includes an absence of instrumental rationality on the part of democratic citizens. For this reason, taxation presents a persistent problem for any concept of self-government, and may usefully be regarded as a technology of the self, conventional with democracy but at most ambiguous in its capability to be genuinely democratic, both theoretically and practically.