Aristotle

Ancient Greek philosopher — student of Plato — founder of the Lyceum — who created formal logic, founded comparative biology, wrote foundational texts in ethics (Nicomachean Ethics), politics, rhetoric, poetics, and physics — whose works dominated Western thought for 2000 years.

Creates the category system and formal logic that structured Western thought — Aristotle's syllogistic logic, his categories (substance, quality, quantity, etc.), and his teleological biology dominated the intellectual framework of Europe from Augustine through the late Middle Ages; his Nicomachean Ethics is the foundational text of virtue ethics.