The concept of ‘social brain’ is a hybrid, located somewhere in between politically motivated philosophical speculation about the mind and its place in the social world, and recently emerged inquiries into cognition, selfhood, development, etc., returning to some of the founding insights of social psychology but embedding them in a neuroscientific framework. In this paper I try to reconstruct a philosophical tradition for the social brain, a ‘Spinozist’ tradition which locates the brain within the broader network of relations, including social relations. This tradition runs from Spinoza to Lev Vygotsky in the early 20th century, and on to Gilles Deleuze, Toni Negri and Paolo Virno in recent European philosophy, as a new perspective on the brain. The concept of social brain that is articulated in this reconstruction – some early-20th century Soviet neuropsychologists spoke of socialism and the cortex as being “on the same path” – overcomes distinctions between Continental thought and the philosophy of mind, and possibly gives a new metaphysical framework for social cognition.