Although described in Aristotelian terminology, the belief in progress is completely different from the attitude of Aristotle and the whole ancient world. In Aristotle the movement from potentiality to actuality is vertical, going from the lower to the higher forms of being. In modern progressivism the movement from potentiality to actuality is horizontal, temporal, futuristic. And this is the main form in which the self-affirmation of modern Western humanity manifested itself. It was courage, for it had to take into itself an anxiety which grew with the growing knowledge of the universe and our world within it.