Steiner's work includes both universalist, humanist elements and historically influenced racial assumptions. Due to the contrast and even contradictions between these elements, "whether a given reader interprets Anthroposophy as racist or not depends upon that reader's concerns". Steiner considered that by dint of its shared language and culture, each people has a unique essence, which he called its soul or spirit. He saw race as a physical manifestation of humanity's spiritual evolution, and at times discussed race in terms of complex hierarchies that were largely derived from 19th century biology, anthropology, philosophy and theosophy. However, he consistently and explicitly subordinated race, ethnicity, gender, and indeed all hereditary factors, to individual factors in development. For Steiner, human individuality is centered in a person's unique biography, and he believed that an individual's experiences and development are not bound by a single lifetime or the qualities of the physical body. More specifically: