The article presents a conception of the theoretical framework of the term 'discourse' in sociology exemplified by the sociology of nationality. The conception was defined explicitly and verified in the research concerning regional and national identity of inhabitants of Silesia. The intention of the author is to concentrate mainly on public discourse, which does not exclude the analysis of the importance of the ordinary conversations for forming discourse as such. Subjects of public discourse as well as the matter of discourse analysis are characterized with special attention paid to their mutual relationships and preferred research methods. The author makes use of the achievements of the science of communication and linguistics, especially text linguistics. Discourse consists of a net of keystones that interact and strengthen each other. Understood in that way it is given a historical dimension through the introduction of the category of 'trajectory'. Due to the fact that the structure of discourse (a net of keystones) corresponds to the structure of social memory of senders and receivers, some keystones refer to the resources of cultural, social, scientific and symbolic capital of the social world. On the basis of discourse social identity is formed and, to some extent, new identity is created as well. The conception presented above is analyzed and exemplified by the formation of regional and national identity of the inhabitants of Silesia.