Book excerpt: With contributions from Anne Alvarez, Joshua Durban, Jeffrey L. Eaton, Bernard Golse, Didier Houzel, Howard B. Levine, Suzanne Maiello, Sylvain Missonnier, Bernd Nissen, Marganit Ofer, and Jani Santamaria. The capacity to create psychic representations is now understood to be a developmental achievement. Without it, meaning cannot be ascertained and this can lead to "psychic voids" and "unrepresented states", which can contribute to the development of autism and autistic spectrum disorders (ASD). Unrepresented states are also implicated and encountered in other, non-autistic, non-neurotic conditions, such as psychosomatic disorders, addictions, perversions, and primitive character disorders. The affects that unrepresented states produce or are associated with are often those of terror, emptiness, annihilation and despair. The organisation of the psyche consists of psychotic - i.e. unstructured - as well as neurotic parts of the mind; unintegrated as well as integrated areas; and unrepresented areas with little meaning as well as represented states consisting of specific ideas imbued with affect. Given this organisation, we should expect to find both an unstructured and a dynamic unconscious in all patients. This implies that, to some degree, unrepresented and unintegrated states are universal and will exist and be encountered in all of us. Consequently, the opportunities and challenges presented by the understanding and treatment of autism and ASD, where the unrepresented and its consequences (e.g. defensive organisations employed to protect against annihilation anxiety and catastrophic dread) can be encountered may offer us metaphors and clues relevant to aspects of the treatment of all patients, no matter what their dominant diagnoses may be. Packed with theory and helpful case studies, this carefully edited collection from an international array of experts in the field is essential reading for all practising clinicians.