A material-semiotic theory of social action. Developed by the sociologists Bruno Latour, Michel Callon, and John Law at the Centre de Sociologie de l’Innovation at the École Nationale Supérieure des Mines de Paris in the early 1980s as a means of explaining the conditions for the emergence of innovation. It is characterized by its treatment of people, things, and ideas as actant, recognizing that all three are capable of initiating and sustaining an action; it also emphasizes that actants are incapable of performing most actions by themselves, but require the support of a network of other actants; similarly, actants are needed to keep networks going. Perhaps the most striking use of this type of thinking is Dutch architect Rem Koolhaas’ Delirious New York (1994), which, in apparent ignorance of actor network theory, produced a striking account of the development of New York which claimed just three things were crucial to its present-day look: the laying out of the city grid, the invention of the elevator, and the building code restrictions with regard to the casting of shadows. Actor network theory is particularly useful for identifying the critical components of a particular business enterprise or a whole sector, but finds it difficult to deal with more open-ended institutions such as culture and society.