Aristotle (384–322 BC) was a Greek philosopher and scientist — a man who tried to explain the world by looking carefully and then thinking hard. He was a student of Plato, and later he taught Alexander the Great. His works cover science, politics, morality, and literature. Western schools leaned on him for a very long time; for hundreds of years, “what Aristotle said” was treated almost like a rule. Though actually, some of his science is wrong by today's lights — he did not have today's tools — but the habit of asking “what kind of thing is this?” and “what is it for?” still shapes how people argue. In English, Aristotle is a name, so we capitalise it.