Zeno of Elea was a Greek philosopher known for his paradoxes. He lived in the 5th century BCE and is considered one of the founders of dialectic, a method of philosophical inquiry. His most famous paradox is the Achilles and the Tortoise, which states that a tortoise can never be overtaken by a runner, no matter how fast the runner is. Zeno's paradoxes were meant to challenge accepted notions of space and time.