In formulating attachment theory, Bowlby made a number of important conceptual contributions to our understanding of human development. Discussed here are the balance (rather than the conflict) between attachment and exploration, the concept of internal working models, and the parent as a psychological secure base. In addition, Bowlby's theory of reality is examined, integration of Bowlby's and Erikson's ideas regarding attachment and culture is suggested, and Bowlby's open-minded approach to theory construction is acknowledged.