This paper uses the logic derived by Matte Blanco to provide an Archimedean point and a mathematics, both of which Jung complained of lacking, with which to validate the notion of synchronicity and to demonstrate that it is one of the inevitable properties of an unconscious which is unrepressed such as Jung's collective unconscious, and that such an unconscious will also be affective and interpersonal as well as intrapersonal. These have important clinical implications. After an exposition of Matte Blanco's thinking, some clinical material is presented of an episode in which patient and author both suffered the same psychosomatic symptom some time just prior to a session. Correspondences between Matte Blanco's logically derived ideas and Jung's phenomenological observations are made.