In 356 B.C., Alexander was born into a state that was already in the midst of great change. His father, Philip II, who was largely responsible for these changes, had given Alexander a united Hellenic League over which to rule. As Macedonia had hitherto been looked upon as semi-barbaric, when Philip reorganized the state and conquered Athens and Thebes, the rest of the Greek city-states were reluctant to submit themselves to Macedonian rule. Indeed, though they would succeed in keeping Greece in line, neither Philip nor Alexander ever had the sincere loyalty of his citizens, for Greece could never get past its resentment of Macedonia. Moreover, it did not help the ruler's cause that republicanism–and even democracy–were being explored in the individual city-states. Aristotle must have had a difficult time educating the young prince Alexander to become a monarch when he likely doubted the justice of that position.
Alexander also inherited the legacy of the Persian invasion. His father had long dreamed of the idea of invading Persia but had died before he could achieve it. The roots of the conquest were manifold. Formally, it was carried out to free Greek cities under the rule of Persia and to revenge wrongs done to Greece in the past. Money may also have been a factor, as Alexander was in significant debt and counted on tapping into the opulence of Persia. Perhaps more important, the prevailing sentiment of the times was that non-Greeks were barbarians and deserved to be enslaved. Even the enlightened Aristotle was adamant in this belief, and he educated Alexander to that extent. Alexander himself would depart from his former master, and his desire to cooperate with Persians earned him the resentment of many conservative Macedonians.
Alexander's opposition, then, stemmed from two corners–the Greek city-states, which were constantly looking for a chance to rebel against him, and his own Macedonians, who objected to his attitude toward the Persians. The differences between Persia and Greece were significant in practice as well as theory, which led to many conflicts in the court. Alexander, for his part, made many concessions and adaptations to the Persian way of life, including participation in religious rituals and marriage Persian women–which served only to worsen his unpopularity.
Conquest was Alexander's main–and perhaps only–ambition. He was fortunate that the power of Persia was in decline. He of course preceded the Roman Empire, but the idea of building such an empire was far from new. Most territories were used to the fact of outside rule; some fought and others conceded. It is significant, however, that each territory had to be dealt with individually, for defeating the Great King was not sufficient in itself.
The construction of Alexander's life is itself problematic, for it is difficult to separate fact from legend. In general, historians have had to deduce the truth by evaluating a variety of sources and stories. When uncertainties persist, more than one account must be acknowledged. One of the most famous sources is Plutarch's Lives.