This chapter takes us into the psychodynamic thinking of the pio-neers of dissociation theory: Janet, Freud, Ferenczi, and Fairbairn. Janet was the first to link dissociation with psychological trauma and to articulate a theory of subconscious psychic determinism. He developed a psychodynamic theory premised on multiple centers of consciousness. Although Freud’s early writing reflects the influence of Janet, his own thinking focused on defense from the start. Freud was thinking in terms of dissociation, but he pursued different forms of dissociationism than Janet (Erdelyi, 1994). Four types of Freudian dissociationism are outlined: splitting of consciousness, splits between conscious and unconscious, splits between the ego and the superego, and splits within the ego itself.