Protagoras was a prominent ancient Greek philosopher, known for his contributions to the field of sophistry. He lived during the 5th century BCE and is often credited with the famous statement, "Man is the measure of all things," which suggests that individual perception shapes reality. Protagoras taught that knowledge and truth are subjective, varying from person to person. As a teacher, Protagoras offered education in rhetoric and debate, helping students develop persuasive skills. His ideas influenced later philosophers, including Socrates and Plato, who engaged with his concepts in their own works. Protagoras' legacy remains significant in discussions of relativism and ethics.