From Birth of Reason and Other Essays
My first philosophical enthusiasm was for Catholic theology; I admired, and still admire, that magnificent construction and the spiritual discipline it can inspire; but I soon learned to admire also Hellenistic and Indian wisdom. All religions and moralities seem to me forms of paganism; only that in ages of ripe experience or of decadence they become penitential and subjective.
From Letters of George Santayana
I was christened in the Church and profess no other religion, so that from the point of view of the census-taker I am unmistakably a Catholic. My Protestant and Jewish critics also discover a good deal of Catholicism in my writings; but I have never been a practising Catholic, and my views in philosophy and history are incompatible with belief in any revelation. It would therefore be wholly misleading to classify me among "Catholic Authors".
Letters '55 at 337 ("To Father Matthew Hoehn, O.S.B., August 10, 1939").
From Philosophy of George Santayana
[M]y affection for the Catholic system is justified naturalistically because I regard it as a true symbol for the real relations of spirit within nature.
From Realms of Being
Christianity was thus a fundamentally new religion, a religion of the spirit. It completely reversed the inspiration of the Jews in their frank original hopes, and rather resembled Neo-Platonism and Buddhism. The Jews did well, from their point of view, to reject it, and the Protestants, from theirs, to reform it so as to revert to the cultus of marriage, thrift, science, and nationality. Nevertheless, a religion or philosophy without repentance, without disillusion or asceticism, reckons without its host. The Jews themselves produced Christianity, and the Greeks helped them do it. After all, it is the spirit that makes human nature human; and in the confused, tormented, corrupt life of Christendom, not only do we find many a bright focus of mercy, sanctity, poetry, speculation, and love, but even the tone and habit of the common mind seem shot through with more wit and insight, more merriment and kindness, than in ages and nations that have never asked to be saved.
From Persons and Places: The Background of My Life
Catholicism is the most human of religions, if taken humanly: it is paganism spiritually transformed and made metaphysical. It corresponds most adequately to the various exigencies of moral life, with just the needed dose of wisdom, sublimity, and illusion. Only it should be accepted humanly, traditionally, as part of an unquestioned order, a moral heritage, like one's language and family life, leaving religious controversy to the synods and metaphysical speculation to the schools.
From Persons and Places: My Host the World
Catholicism is paganism spiritualised: it is fundamentally naturalistic; and the transcendental spirit and the wise statesman may accept Catholicism, where it naturally arises, as a good poetic symbol for the forces and the issues of human life in that phase; not, however, as a scientific revelation of reality or a history of literal facts. Religion is valid poetry infused into common life. It is not a revelation truer than perception or than science.