The philosopher who taught Alexander the Great was Aristotle. Aristotle was a Greek philosopher who lived from 384 to 322 BCE. He was a student of Plato and later became the tutor of Alexander the Great, who went on to become one of the most famous military leaders in history.

Aristotle's teachings had a significant impact on Alexander's education and his later actions as a ruler. Here are some key points to explain this further:

1. Aristotle as a Tutor:
- Aristotle was invited by King Philip II of Macedon, Alexander's father, to become the tutor of his son.
- Aristotle accepted the offer and became Alexander's personal tutor from the age of 13 until he was 16.
- During this time, Aristotle taught Alexander a wide range of subjects, including philosophy, science, literature, and politics.

2. Influence on Alexander's Education:
- Aristotle's teachings had a profound influence on Alexander's education and shaped his worldview.
- Aristotle emphasized the importance of reason and logic, encouraging Alexander to think critically and make informed decisions.
- He also taught Alexander about ethics and morality, emphasizing the importance of virtue and self-control.

3. Scientific and Philosophical Knowledge:
- Aristotle's teachings in science and philosophy had a lasting impact on Alexander's intellectual development.
- Aristotle introduced Alexander to various scientific disciplines, including biology, astronomy, and physics.
- Alexander's interest in natural history and exploration can be traced back to his exposure to Aristotle's teachings in these fields.

4. Political and Leadership Lessons:
- Aristotle's teachings on politics and leadership also played a crucial role in shaping Alexander's approach to governance.
- Aristotle emphasized the concept of the "ideal ruler" and the importance of ruling for the benefit of the people.
- Alexander's later actions as a ruler, including his efforts to blend Greek and Persian cultures and his attempts to create a unified empire, can be seen as influenced by Aristotle's political teachings.

In conclusion, Aristotle was the philosopher who taught Alexander the Great. His teachings had a significant impact on Alexander's education and later actions as a ruler. Aristotle's emphasis on reason, ethics, science, and politics shaped Alexander's intellectual development and his approach to leadership.