Rudolf Steiner (25 or 27 February 1861 - 30 March 1925) was an Austrian philosopher, social thinker, architect and esotericist. He gained initial recognition as a literary critic and cultural philosopher. At the beginning of the twentieth century, he founded a new spiritual movement, Anthroposophy, as an esoteric philosophy growing out of European transcendentalist roots with links to Theosophy.

Steiner led this movement through several phases. In the first, more philosophically oriented phase, Steiner attempted to find a synthesis between science and mysticism; his philosophical work of these years, which he termed spiritual science, sought to provide a connection between the cognitive path of Western philosophy and the inner and spiritual needs of the human being. In a second phase, beginning around 1907, he began working collaboratively in a variety of artistic media, including drama, the movement arts (developing a new artistic form, Eurythmy) and architecture, culminating in the building of a cultural center to house all the arts, the Goetheanum. After the First World War, Steiner worked with educators, farmers, doctors, and other professionals to develop Waldorf education, biodynamic agriculture, anthroposophical medicine as well as new directions in numerous other areas.

Steiner advocated a form of ethical individualism, to which he later brought a more explicitly spiritual component. He based his epistemology on Johann Wolfgang Goethe's world view, in which "Thinking ... is no more and no less an organ of perception than the eye or ear. Just as the eye perceives colours and the ear sounds, so thinking perceives ideas." A consistent thread that runs from his earliest philosophical phase through his later spiritual orientation is the goal of demonstrating that there are no essential limits to human knowledge.