In this collective volume the origins, neurosocial support, and therapeutic implications of (pre)verbal intersubjectivity are examined with a focus on implications of the discovery of mirror neurons. Entailing a paradigmatic revolution in the intersection of developmental, social and neural sciences, two radical turnabouts are entailed. First, no longer can be upheld as valid Cartesian and Leibnizian assumptions about monadic subjects with disembodied minds without windows to each other except as mediated by culture. Supported by a mirror system, specified in this volume by some of the discoverers, modes of participant perception have now been identified which entail embodied simulation and co-movements with others in felt immediacy. Second, no longer can be retained the Piagetian attribution of infant egocentricity. Pioneers who have broken new research grounds in the study of newborns, protoconversation, and early speech perception document in the present volume infant capacity for interpersonal communion, empathic identification, and learning by altercentric participation.