  Morgenthau systematizes realism in international relations on the basis of six principles that he includes in the second edition of Politics among Nations. As a traditionalist, he opposes the so-called scientists (the scholars who, especially in the 1950s, tried to reduce the discipline of international relations to a branch of behavioral science). Nevertheless, in the first principle he states that realism is based on objective laws that have their roots in unchanging human nature (4). He wants to develop realism into both a theory of international politics and a political art, a useful tool of foreign policy.