Second-generation cultural-historical activity theory, which drew its inspiration from Leont'ev's work, constituted an advance over Vygotsky's first-generation theory by explicitly articulating the dialectical relation between individual and collective. As part of an effort to develop third-generation-historical activity theory, I propose in this article a way in which emotion, motivation, and identity can be incorporated into the theory. I provide case materials from a 5-year ethnographic research project in a salmon hatchery that underscores the important role emotion and the derivative phenomena of motivation and identity play in the workplace generally, and in mathematical knowledgeability particularly. (Contains 10 footnotes and 6 figures.)