Santayana's philosophic stance has been given the apparently opposite descriptions of materialism and Platonism. The contradiction is partly understandable as resulting from his view of the mind as being firmly placed in and responsive to a physical, biological context, and his simultaneous emphasis on and high evaluation of the mind's rational and imaginative vision of physical reality. In an important early work, The Sense of Beauty (1896), he enunciated a qualified hedonism that placed high value on aesthetic pleasure; it was a pleasure that was understood to be an irrational expression of vital interests but was distinguished from direct, sensual pleasures.
The Life of Reason (1905–6) investigates the mind's evolving attempts to define its relationship to its natural context. In that work he saw the relationship of thought and reality as one of ideal correspondence. Santayana's earlier work is marked by a psychological approach to the life of the mind. With the publication of Scepticism and Animal Faith (1923) and The Realms of Being, a four-volume work ( The Realm of Essence, 1927; The Realm of Matter, 1930; The Realm of Truth, 1937; The Realm of Spirit, 1940; 1-vol. ed. 1942), he adopted a more classical philosophic approach, making ontological distinctions between the objects of mental activity. Against Cartesian skepticism and idealism he advanced the notion of "animal faith" as the basis of the life of reason.
Religion he viewed as an imaginative creation of real value but without absolute significance. Although he continued to value imaginative and rational consciousness he warned against the mind's tendency to confer substantial reality and causal efficacy on its own creations. His personal withdrawal from active life was paralleled in his philosophy by a decided moral detachment. The whole of Santayana's philosophic writing displays a characteristic richness of style; he also wrote poetry, a volume of which appeared in 1923. His only novel, The Last Puritan (1935), had great popular success. His Dominations and Powers, on political philosophy, was published in 1951.