This one comes from ALEXANDER OF MACEDON, 356-323 B.C.
A Historical Biography by Peter Green.
[Alexander’s father] Philip’s training for power was proceeding along useful if unorthodox lines. His experience as a member of the Macedonian royal household had given him an understandably cynical view of human nature: in this world murder, adultery and usurpation were commonplace, as liable to be practiced by one’s own mother as by anyone else. In later life Philip took it as axiomatic that all diplomacy was based on self-interest, and every man had his price: events seldom proved him wrong. [Italics added.] In Thebes he saw, too, the besetting weaknesses of a democratic city-state—constant party intrigue, lack of a strong executive power, the inability to force quick decisions, the unpredictable vagaries of the assembly at voting-time, the system of annual elections which made any serious long-term planning almost impossible, the amateur ad hoc military levies (though here Thebes was better off than, say, Athens). For the first time he began to understand how Macedonia’s outdated institutions, so despised by the rest of Greece, might prove a source of strength when dealing with such opponents. Throughout his life he gained his greatest advances by exploiting human cupidity and democractic incompetence—most often at the same time. [Italics added.]