This paper introduces the critical theory of Jürgen Habermas by presenting it as a response to the problems of relativism. While relativism offers a critique of power abuse, it has the additional effect of undermining the use of reason in political and moral action. Habermas seeks to preserve its strengths, and at the same time to defend a role for reason. Following an exploration of the gains offered by his approach, it is suggested that, though his treatment for relativism is effective, it too has a side-effect.