Celine Surprenant's study examines the term mass in Freud's writings, and shows that it denotes less a type of human grouping than a preoccupation with quantity, one of the key concepts in Freud's theory of the psyche. When psychoanalysis turns its attention to the many, it is indeed confronted with fundamental epistemological questions, concerning the scientific status of its concepts or the analogical and metaphorical procedures that underlie the analysis of society. From the moment that quantity becomes attached with 'large scale phenomena', it poses enormous difficulty to the Freudian theory of the mind. The book offers an original contribution to Freudian studies by demonstrating that the problem of the mass, rather than standing as an exclusive socio-political concern, touches upon the question of the philosophical relevance of Freud. Focussing on this neglected term allows the author to raise anew the question of the 'application' of psychoanalysis, beyond a mechanistic understanding of this term and of Freud's writings.