Philosophy, politics and contestability

The essential contestability thesis continues to enjoy widespread support, and has been invoked as an explanatory fact in analysing ideological morphology. This paper argues, however, that the general form of the thesis faces incoherence or failure: it violates plausible constraints on concept-possession, and is forced to rely either on an esoteric doctrine which shortcircuits the thesis's original explanatory rationale, or on an error theory which cannot do the explanatory job the thesis requires. The thesis started by aiming to explain a common political phenomenon, that of endemic disagreement, but is forced to turn away from the world of politics towards ideal theory. The limit of explanation is reached when we apply the thesis to the concept of politics itself. For the point of essential contestability was to understand political disagreement, and if the thesis is true of politics itself, it is not clear how the explanandum can even be specified. This casts doubt on the viability of political design, the characteristic project of modern philosophical liberalism, since it is not clear that the project can even be coherently specified in advance of politics.