The rapid scientific and technological advances of recent centuries have profoundly changed humanity’s understanding of itself. Through their scientific revolutions, Copernicus and Darwin transformed the conception of the human being: “The Earth is not the center of the universe” and “The human being is also only an animal.” Today, the fields in which questions concerning human nature and the need for ethical limits are most intensively debated include biogenetics, where the human genome can be copied and altered; medical ethics, including assisted suicide and preimplantation genetic diagnosis; brain research, which raises the question of how free the human will is;