Existentialist way of thinking, it seems, is timeless; Existentialist thought has been identified in Heraclitus, Socrates, and even in Augustine. Modern existentialism, however, is identified with the thought of five thinkers: Kierkegaard, Nietzsche, Heidegger, Camus, and Sartre. The wide difference in the religious and political thought of these five philosophers is something that makes it difficult to see existentialism as a school based on a doctrine or worldview. Kierkegaard was religious; Nietzsche and Sartre were atheists. Kierkegaard would have nothing to do with politics, he was disgusted by it, but Sartre, Camus, and Heidegger were not only political theorists but also political activists. Sartre was a Marxist; Camus was an anti-Marxist and identified as a humanitarian. Heidegger, it's alleged, was close to Nazism. Instead of a common doctrine and worldview, existentialism is a movement based on certain sensibilities regarding individualism and human freedom. The philosophy sees Dostoevsky and Kafka as its own thinkers.