Our goal in this series of four papers is a further refinement of a theory of interaction for psychoanalysis, with a specific focus on the concept of intersubjectivity. Psychoanalysis has addressed the concept of intersubjectivity primarily in the verbal/explicit mode. In contrast, infant research has addressed the concept of intersubjectivity in the nonverbal/ implicit mode of action sequences, or procedural knowledge. We propose that an integration of explicit/linguistic with implicit/nonverbal theories of intersubjectivity is essential to a deeper understanding of therapeutic action in psychoanalysis today. To shed light on an implicit/nonverbal