In the course of evolution, people invented increasingly complex forms and patterns of social and cultural interaction, cooperation and communicative coordination. At the same time, equally complex forms and patterns of self-awareness, consciousness and the ability to speak developed. Within the framework of a systemic-development-oriented theory of the interpersonal, the phenomena mentioned can be considered together. What distinguishes us as a species emerges from social coexistence and develops within the framework of mutually shaping relationships. We are relationship-creating actors who observe each other while observing and shaping relationships, and we have learned to shape relationships creatively. A general theory of how human relationships are formed has so far been lacking. It is justified here in terms of evolutionary and developmental psychology. An overarching theoretical perspective that expands the field of vision towards a consistently relationship-oriented perspective. A scientifically sound, yet easy to read and excitingly written basic work for counselling, therapy and supervision.