How can we analyze an instance of public discourse using linguistic methods? What patterns of argumentation and thinking in connection with the subject of the immigration of workers to the Federal Republic remained much the same over a lengthy period of time, what others changed in the course of time, what new ones joined them? To answer these questions, the author substantiates a concept of topic based on argumentation theory, and uses that concept as a category in the 'deep-semantic' analysis of a major text corpus. The empirical analysis indicates how the linguistic construction of the subject of 'migrant workers' developed between 1960 and 1985.