According to Whitehead, symbolic references fulfil an important role not only in human culture and civilization, but also in the process of natural evolution. Contrary to philosophers such as Ernst Cassirer, who think that the process of symbolization is an exclusive characteristic of the human mind and the human being, Whitehead develops his theory of symbolization as part of a natural philosophy. He states his own philosophy of nature as an “introversion of the philosophy” of Kant and as a “critique of pure feeling”. Whitehead criticizes Kant’s thinking and especially his transcendental idealism, because Kant’s theory lacks an explanation of how the subject that is involved in the activity of observing nature develops within the evolutionary process of nature. Whereas Kant simply presupposes the observing subjectivity, Whitehead wishes to explain how the subject emerges as a result of an evolutionary process in a self-creating nature. In this creative process, symbolism is a fundamental aspect. The assumption that there are two modes of “perceptive experience” is a special characteristic of Whiteheads theory of symbolism. Following this assumption, higher organisms not only have experiences in the mode of senseperception but also in the mode of what Whitehead calls “causal efficacy”. In the United States, Whiteheads most famous students, Susanne K. Langer and Nelson Goodman continued to develop his theory of symbolism, thus transforming it. In Germany, the philosopher Oswald Schwemmer pointed out the relevance of this theory for the philosophy of culture.