Castells' analysis of the rise of a global network society and information age is underpinned, paradoxically, by a nationalist vision with organic links in a Gramscian sense to Catalan nationalism. This leads to various weaknesses in his theory, especially an over-emphasis on language and nation at the expense of class. Exploring the specifically Catalan origins of his work, and testing its adequacy there, helps us to understand Castells' broader approach. Discussion of Castells has perhaps overlooked his commitment to nationalism because the sociology of identity sometimes unwittingly adopts what Billig has called a banal nationalist perspective. A stricter distinction between the different meanings of the term identity would help sociology to avoid arguments, such as that of Castells, that risk becoming determinist, teleological or both. The article concludes by asking whether the 'sociological imagination' has been alert enough to its banal nationalist form, facilitated by its intimate relationship with the state, its concern for policy relevance and methods of data gathering.