Following the work of Charles Mills, Engelhardt argues that ideal theories adopt oppression-obscuring assumptions while nonideal theories avoid them (or at least try to). Ideal theories assume that language users are basically equal, and that social institutions and structures are basically just, but scholarship on Western social relations, institutions, and structures shows that in fact each of these is systematically influenced by oppression. Consequently, ideal theories tend to be systematically inaccurate. Moreover, since oppression systematically produces ignorance of systemic oppression, such systematically inaccurate theories are likely the norm rather than the exception.
Engelhardt shows that once we've shown that oppression systematically influences the processes that determine linguistic meanings (according to content externalism), then we have reason to expand our notion of hermeneutical injustice, we have evidence that hermeneutical injustice occurs systematically, and we have grounds for expanding discussions of conceptual engineering to include questions about engineering the processes that determine concepts, not just concepts themselves.