Machiavelli's philosophy is based on his pessimistic view of human nature. He has been called a "pagan Augustinian". Aristotle and Plato also called attention to the imperfect nature of man, but Machiavelli rejected their approach. He follows Xenophon more closely. It was Xenophon who took a rational organization, the army, and applied the lessons learned in its construction and operation to the problems of society in general. Machiavelli follows his lead in linking military and civil societies. He goes a step beyond Xenophon when he applies the lessons of military practice to the internal affairs of his civic body. For all his recognition of the failings of human nature, Xenophon could not free himself from the Greek distinction between friend and foe. For him coercion was to be applied to the enemy, and both the army and the polis were to be based on friendship. Machiavelli does not recognize this distinction. To him everyone is a potential enemy, hence the civic rulers must employ the same measures employed by the general to defeat his enemies. This is the reason Machiavelli makes no distinction between the statesman and military commander and why his approach to politics is a military one. Just as the unchanging character of human nature is the stable ingredient which makes the study of history important for the statesman, the presence of man himself at the controls in all human organizations makes the study of his character the basic activity for the successful leader. Machiavelli's state and army are not abstract entities endowed with human characteristics or desires. All decisions are made by men and all evoke reactions in other men. Machiavelli's insistence on this principle is seen in each of the diverse topics included in this study. For him the proper decision to such questions as whether to form alliances or not, when to invade the enemy territory, when to use money, how to acquire and control colonies, how to use "peace" offensives, how to organize a community and whether to appease an aggressor or not are all based on an evaluation of the probable reaction of those humans affected by the decision. Likewise, his criteria for the selection of a leader and his precepts to guide the leader's actions in command of an army are based on principles of psychology. The reaction of the army is itself governed by an evaluation of the human material available to the leader. Such considerations as the proper type of soldier, the discipline to be developed, the training program to be followed, the most useful armament, the correct logistical procedures, and the proper role of infantry, cavalry and artillery are all made under the assumption that man has been, is, and always will be the central and essential weapon in war.