There are many grounds for arguing that people with a range of disabilities have more in common than they have differences. However, those grounds to date have not resulted in a unified social movement. This paper examines one possible reason for that lack of unity: the particular force of being unreasonable in modern society. However, being unreasonable is not limited to those with a psychiatric diagnosis, nor does a lack or loss of reason take a simple common form within that group: it is a highly nuanced and context-specific matter. This complexity is discussed in relation to a set of inter-related questions about legalism, morality and post-enlightenment concerns with order and rationality. The paper concludes with a discussion of scenarios available to new social movements concerned with disability.