Ecopsychology is an interdisciplinary and transdisciplinary field that focuses on the synthesis of ecology and psychology and the promotion of sustainability. It is distinguished from conventional psychology as it focuses on studying the emotional bond between humans and the Earth. Instead of examining personal pain solely in the context of individual or family pathology, it is analyzed in its wider connection to the more than human world. A central premise is that while the mind is shaped by the modern world, its underlying structure was created in a natural non-human environment. Ecopsychology seeks to expand and remedy the emotional connection between humans and nature, treating people psychologically by bringing them spiritually closer to nature. In his 1929 book Civilization and Its Discontents ("Das Unbehagen in der Kultur"), Sigmund Freud discussed the basic tensions between civilization and the individual. He recognized the interconnection between the internal world of the mind and the external world of the environment, stating:Our present ego-feeling is, therefore, only a shrunken residue of a much more inclusive—indeed, an all-embracing—feeling which corresponded to a more intimate bond between the ego and the world about it. Influenced by the philosophies of noted ecologists Walles T. Edmondson and Loren Eiseley, Robert Greenway began researching and developing a concept that he described as "a marriage" between psychology and ecology in the early 1960s. He theorized that "the mind is nature, and nature, the mind," and called its study psychoecology. Greenway published his first essay on the topic at Brandeis University in 1963. In 1969, he began teaching the subject at Sonoma State University. One of Greenway's students founded a psychoecology study group at University of California, Berkeley, which was joined by Theodore Roszak in the 1990s. In the 1995 book Ecopsychology: Restoring the Earth, Healing the Mind, Greenway wrote:Ecopsychology is a search for language to describe the human-nature relationship.