This is the fourth part in the six linked podcasts on hegemony and populism, focusing solely on Ernesto Laclau's 'On Populist Reason'. The discussion takes the book chapter by chapter, starting with his critique of early crowd psychology, moving on to the impact of Freud's group psychology, with which Laclau uses to begin outlining his technical framework for his theory of populism. A central element to this theory is the notion that a social will to other exists, and this can be channelled down at the vulnerable by a right-wing populism or channelled up at power by the left. Laclau then develops his theory in terms of the empty signifiers that operate as the thing in which identity is invested in and moves people to act one way or ther other, and, returning to the critique of crowd psychology, adds that populism is essential to democracy.