The concept of intersubjectivity may be used to illuminate the way in which we observe and describe many of the interpersonal processes that begin in infancy. The more traditional psychoanalytic ideas of holding and containment, as well as relatively recent concepts such as attunement and reflective function, can be seen as belonging within this coexisting area of experience. Intersubjectivity has contributed to human evolution and has a neurological foundation based on mirror neurons; it provides a perspective on psychotherapy (especially within infant mental health) that can oversee the internal worlds of mutually influencing experience. (Contains 2 notes.)