Final answer:
Plato's major philosophical contribution was his Theory of Forms, which distinguishes between the material world and a higher reality of perfect, immutable forms. He believed philosophers could access this reality through reason, and he outlined his vision for a society guided by philosopher-kings in his work The Republic.
Step-by-step explanation:
Plato's Major Contribution to Philosophy
Plato's major contribution to philosophy was his Theory of Forms, which proposed that the material world we perceive through our senses is merely an illusion, a shadow of the true reality. This higher reality consists of unchangeable, perfect forms that exist in an intellectual realm. Plato believed that the philosopher's role was to use reason to understand these forms, which are the essence of truth, beauty, justice, and wisdom. His work laid the groundwork for Western philosophy, integrating and expanding upon ideas from Socrates, the Sophists, and Pythagoreans. In The Republic, Plato describes an ideal society ruled by philosopher-kings, emphasizing the importance of education and contemplation in achieving philosophical wisdom and political power.