An ethnographic study of the words and actions common to a shelter for people considered homeless and mentally ill shows how distinct forms of reasoning and personal agency relate to a set of practical concerns and political exigencies. Whereas the shelter's staff rely on and promote a referential language and direct, active forms of agency, its residents depend on tactical, persuasive uses of language and oblique, reactive forms of agency. Yet because the staff have the upper hand politically, their orientations to language, thought, and action take a more central role in encouraging people to act in sincere and reasonable ways. The residents draw on ideas of sincerity, reason, and personal accountability, but in makeshift ways, with the result that the ideas are caught up in the rhetoric of self-presentation. The article's findings underscore the need for anthropologists to attend to the diverse means, and political, linguistic, and cultural grounds, of human reason and agency. [agency, reason, language, power, mental illness, homelessness]