Traumatic aspects of the lives of John Bowlby and Margaret Mahler can be seen to inform their intellectual careers, a perspective that suggests that attachment theory and separation-individuation theory are far more consonant with one another than otherwise. Articulating the domains of convergence between the two theories reveals the essential complementarity of the special strengths of each. Both theories were attempts to understand the role of experience in the development of mental representations. Mahler paid close clinical attention to inner mental states and their evolution, while Bowlby searched for behavioral correlates that could lend themselves to empirical observation and inferences about internal representations.