- Thales of Miletus (624-546 BCE): Considered the first philosopher, he believed that all things were composed of a single substance, water.
- Anaximander (610-546 BCE): Proposed that the Earth was a cylinder suspended in space and that the universe was infinite.
- Anaximenes (585-528 BCE): Argued that air was the primary substance and that everything was created by the condensation and rarefaction of air.
- Pythagoras (570-495 BCE): Founded a school of thought that emphasized mathematics and music as the keys to understanding the universe.
- Empedocles (490-430 BCE): Proposed that all things were composed of four elements: earth, air, fire, and water.
- Democritus (460-370 BCE): Developed an atomic theory of matter, stating that all things were composed of tiny, indivisible particles called atoms.
- Hippocrates (460-377 BCE): The "father of medicine," he emphasized the importance of observation and experience in diagnosing and treating illness.
- Plato (427-348 BCE): A student of Socrates, he founded the Academy in Athens and developed a theory of forms, which held that the material world is a mere reflection of a perfect, eternal realm of ideas.
- Aristotle (384-322 BCE): A student of Plato, he founded the Lyceum in Athens and made important contributions to logic, biology, and ethics.
Ancient India (600-200 BCE)
- The Upanishads: A collection of philosophical texts that emerged around 600 BCE, the Upanishads focus on the nature of reality, the self, and the relationship between the two.
- The Buddha (563-483 BCE): Siddhartha Gautama, known as the Buddha, founded Buddhism, which emphasizes the importance of mindfulness, meditation, and the pursuit of enlightenment.
- Patanjali (200 BCE): Authored the Yoga Sutras, a foundational text of yoga philosophy that outlines the eight limbs of yoga as a path to spiritual liberation.
Ancient China (600-200 BCE)
- Confucius (551-479 BCE): A philosopher and teacher, Confucius emphasized the importance of social harmony, respect for elders, and the cultivation of virtue.
- Laozi (6th century BCE): Authored the Tao Te Ching, a foundational text of Taoism, which emphasizes the importance of following the natural order of the universe and achieving a state of wu wei (non-action).
- Mozi (470-391 BCE): Founded Mohism, a philosophy that emphasized the importance of universal love, impartiality, and the rejection of aggression.