1. Santayana. 1900. Interpretations of Poetry and Religion. Ed. William G. Holzberger, and Herman J. Saatkamp Jr. Cambridge, MA: MIT Press, 1989. Cited as IPR.
2. ———. 1905. The Life of Reason: Introduction and Reason in Common Sense. Ed. Martin Coleman, and Marianne Wokeck. Cambridge, MA: MIT Press, 2011. Cited as LR1.
3. ———. 1906. The Life of Reason: Reason in Science. Ed. Martin Coleman, and Marianne Wokeck. Cambridge, MA: MIT Press, 2016. Cited as LR5.
4. ———. 1918. Literal and Symbolic Knowledge. Journal of Philosophy 15: 421–444. Cited as LSK.
5. ———. 1920. Three Proofs of Realism. In Essays in Critical Realism: A Co-operative Study of the Problem of Knowledge, ed. Drake Durant, 163–184. London: Macmillan. Cited as TPR.