1920 Santayana begins spending winters in Rome; continues to summer in Paris, Ávila, Glion, at Lake Geneva, or Cortina d’Ampezzo. Character and Opinion in the United States published. “Three Proofs of Realism” published in Essays in Critical Realism: A Cooperative Study of the Problems of Knowledge.

1922 Soliloquies in England and Later Soliloquies published. Revised second edition of the five books of The Life of Reason published.

1923 “The Unknowable” delivered as the Herbert Spencer Lecture at Oxford in October. Scepticism and Animal Faith and the last collection of Santayana’s poetry to appear during his lifetime, Poems: Selected by the Author and Revised, are published in May and April respectively.

1924 Santayana declines Professor George Herbert Palmer’s invitation to read the Phi Beta Kappa poem at the Harvard Commencement exercises. A revised version of his tragedy (originally published in 1900) is published as Lucifer; or the Heavenly Truce: A Theological Tragedy, by Dunster House, at Cambridge, Massachusetts.

1925 Dialogues in Limbo published during the summer.

1927 Santayana meets Daniel Cory (age 22), who will become his assistant and friend. Platonism and the Spiritual Life published in April. The Realm of Essence: Book First of Realms of Being published in November.

1928 Santayana declines offer of the Norton Chair of Poetry at Harvard for 1928–29. Half-sister Susana dies in Ávila, on 10 February, at age 77.