The Pre-Socratics, ancient Greek thinkers from the 6th-5th centuries BCE, laid the foundation for Western philosophy. They sought rational explanations for the world, moving away from mythological accounts and exploring fundamental questions about reality, knowledge, and existence. Key figures like Thales, Anaximander, and Pythagoras proposed theories about the nature of the universe, while Heraclitus and Parmenides grappled with concepts of change and permanence. Their ideas influenced later philosophers and continue to resonate in modern science and philosophy.