Answer
Plato, the esteemed Greek philosopher, profoundly influenced Santayana's philosophical outlook. Santayana's admiration for Plato's idealism, particularly his theory of Forms, is evident throughout his works. Plato's exploration of the distinction between the sensible and intelligible worlds resonated deeply with Santayana, shaping his own philosophical inquiries into the nature of reality and the relationship between the physical and spiritual realms.