Based on key sutras of Mahayana Buddhism, the foundations of a psychology within the epistemological framework of Buddhism are developed. In addition to writings from three systems of Mahayana - Yogacara, Madhyamaka, and Huayan - the elaboration and direct practical relevance of these foundations in Zen Buddhism are emphasized. Two essential characteristics of Buddhist psychology are interdependence and intersubjectivity. These are reflected in all questions regarding the constitution of the individual, which, from a Buddhist perspective, can only be understood through one's relational experiences. Furthermore, the ethical relevance of Mahayana Buddhist psychology and a comparison with psychoanalytic approaches to human relationships are presented. In dialogue with Buddhism, new possibilities emerge for perceiving the individual in its entirety.