We argue that the proper context for understanding Collingwood’s The Principles of Art is his claim that it has bearing “upon the condition of art in England in 1937”. We thus argue that he formulated a philosophical argument that underpins avant-garde dramatic poetry and theatrical practices (Eliot, Auden and the Group Theatre), taking his interpretation of Spinoza’s Ethics 5 prop. 3 to be the book’s central thesis: it is through art that one knows, against the ‘corruption of consciousness’, what emotions (...) one feels and recognizes them as one’s own. Collingwood further believed that this could only be achieved through collaboration between the artist and the community, validating new theatrical practices involving interaction with the audience. We analyse these views in the context of England in 1937: in an era marked by the rise of Fascism and Nazism, Collingwood believed that art thus conceived could help restoring emotional support for the defense of liberal democracies. We conclude with an exploration of parallels with and divergences from the Spinozist idea of ‘mobilizing affects’ in contemporary ‘left populism’ (Mouffe). (shrink)