At first glance, the only thing that Pierre Macherey and Paolo Virno have in common is that they are, in my opinion, underrated as philosophers. They are both the less well known member of a school, or orientation that is primarily identified with other figures more often discussed; Macherey is often seen as one of the names associated with Althusser, but not referenced as much as Etienne Balibar or even Jacques Rancière and Virno with autonomia or post-operaism, but less famous than Antonio Negri and less infamous than Mario Tronti. Macherey is barely translated into English, but thanks to Seagull books, most of Virno's work is available. The other, more interesting thing that they have in common, is that they have both turned to the concept of labor power as a philosophical concept.
