This essay is premised on two assumptions: first, that concepts change their meaning; second, that the examination of the relationship between language and action - two central components of the public sphere - illuminates the process of change. Three models of conceptual change are critically discussed through their language-action axis. The first, adduced by German historian of concepts Reinhart Koselleck, assumes that conceptual change results from a gap between language and action. The second, put forward by historian of political thought Quentin Skinner, argues that conceptual change is produced by political theorists that are doing something when writing; language, according to this model is (sometimes) a form of action. The t...