Answer:
The main reason was the revolt of his army. Fearing the prospect of facing other large armies and exhausted by years of campaigning, Alexander's army mutinied at the Hyphasis River (Beas), refusing to march farther east.
Explanation: Goooooooogle. Credit to gooooogle.
Are you Australian? In that case it would rather ironically be the Aboriginals and their children. If not, (and I'm not 100 percent sure about this one) but this was during the time period of the African American rights Reform period in the United States.
The answer is utilitarianism
