Steiner advocated a form of ethical individualism, to which he later brought a more explicitly spiritual approach. 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.