Near the end of Alexander's life, he began to suspect plots, and threatened Aristotle in letters. Aristotle was vocal about his dislike for Alexander's claim of divinity, and the king executed Aristotle's grandnephew Callisthenes as a traitor. Alexander died in Babylon in 323 without ever having returned to his native land. Upon Alexander's death, anti-Macedonian sentiment in Athens once again flared up, and Aristotle fled the city. However, he died in Euboea of natural causes that same year, 322 .