Danish philosophy has a long tradition as part of Western philosophy. Perhaps the most influential Danish philosopher was Søren Kierkegaard, the creator of Christian existentialism. Kierkegaard had a few Danish followers, including Harald Høffding, who later in his life moved on to join the movement of positivism. Among Kierkegaard's other followers include Jean-Paul Sartre who was impressed with Kierkegaard's views on the individual, and Rollo May, who helped create humanistic psychology. Another Danish philosopher of note is Grundtvig, whose philosophy gave rise to a new form of non-aggressive nationalism in Denmark, and who is also influential for his theological and historical works.