The work of mid-twentieth century art theorist Anton Ehrenzweig is explored in this original and timely study. An analysis of the dynamic and invigorating intellectual influences, institutional framework and legacy of his work, Between Art Practice and Psychoanalysis reveals the context within which Ehrenzweig worked, how that influenced him and those artists with whom he worked closely. Beth Williamson looks to the writing of Melanie Klein, Marion Milner, Adrian Stokes and others to elaborate Ehrenzweig's theory of art, a theory that extends beyond the visual arts to music. In this first full-length study on his work, including an inventory of his library, previously unexamined archival material and unseen artworks sit at the heart of a book that examines Ehrenzweig's working relationships with important British artists such as Bridget Riley, Eduardo Paolozzi and other members of the Independent Group in London in the 1950s and 1960s. In Ehrenzweig's second book The Hidden Order of Art (1967) his thinking on Jackson Pollock is important too. It was this book that inspired American artists Robert Smithson and Robert Morris when they deployed his concept of 'dedifferentiation'. Here Williamson offers new readings of process art c. 1970 showing how Ehrenzweig's aesthetic retains relevance beyond the immediate post-war era.