Abstract: The nine types of the Enneagram can be precisely correlated with the successive stages of Margaret Mahler’s separationindividuation process. The psychological experiences at a given stage do not cause our type to form. Rather, our inborn type temperament predisposes us to experience a particularly vivid imprint at our type’s corresponding stage of the developmental process. Looking closely at the interplay between type and developmental experience can help us understand how our unique personalities form atop the substrate of our inborn Enneagram type. In particular, it offers us specific clues as to how and when and why we all, depending upon our type, begin to lose contact with the essential qualities of our true nature. As we learn to reconnect with these essential qualities, we work to complete the “unfinished business” of our early development.