Charles Santiago Sanders Peirce was the adopted name of Charles Sanders Peirce (September 10, 1839 – April 19, 1914), an American philosopher, logician, mathematician, and scientist. Peirce's name appeared in print as "Charles Santiago Peirce" as early as 1890. Starting in 1906 he used "Santiago" in many of his own articles. There is no well-documented explanation of why Peirce adopted the middle name "Santiago" (Spanish for Saint James) but speculations and beliefs of contemporaries and scholars focused on his gratitude to his old friend William James and more recently on Peirce's second wife Juliette (of unknown but possibly Spanish Gypsy heritage).
The stories and the evidence
Peirce in his later years became impoverished. It has been said (see below) that Peirce's motive for adopting "Santiago"—"St. James" in Spanish—as a middle name was gratitude to his old friend William James, who dedicated his Will to Believe and Other Essays in Popular Philosophy (1897) to Peirce, and arranged for Peirce during this period to be paid to give two series of lectures at or near Harvard—one in 1898, one of two in 1903. Then in 1907 James dedicated his Pragmatism to the nominalist John Stuart Mill and omitted Peirce from its list of references for further reading—yet also in that book (in Lecture 2, fourth paragraph) James credits Peirce as the originator of pragmatism. By that time, Peirce was already distinguishing his own scholastic realist brand of pragmatism as "pragmaticism". Still, Peirce had increasing reason for gratitude. Each year from 1907 until James's death in 1910, James wrote to his friends in the Boston intelligentsia, asking that they contribute financially to help support Peirce, a fund which continued after James's death. Peirce reciprocated by designating James's eldest son as his heir should Juliette predecease him.
The claim that Peirce adopted the middle name "Santiago" in gratitude to William James goes back at least to William James's wife Alice, quoted in 1927 by F. C. S. Schiller In one of the last quinquennial catalogues, Peirce changed his middle name from Saunders to Santiago. It was long before I understood that it was a way of calling himself St. James, but there it stands Charles Santiago Peirce. In Quinquennial Catalogue of the Officers and Graduates of Harvard University, Peirce appears as "Charles Sanders Peirce" in 1890, 1895, 1900, and 1905. He appears as "Charles Santiago Sanders Peirce," "Charles S. Sanders Peirce," "Charles Sanders Peirce", in 1910 and 1915.
Collected Papers of Charles Sanders Peirce (CP), Volume 5 in 1934 reprinted a comment by Peirce "Mr. Peterson's Proposed Discussion" complete with the name "Charles Santiago Sanders Peirce" appended, first published in The Monist in 1906. The CP editors (Charles Hartshorne and Paul Weiss) added in a footnote, "The additional name Santiago, St. James in Spanish, was adopted by Peirce about this time, apparently in honor of his life-long friend, William James." Weiss also said much the same in the Peirce entry in the Dictionary of American Biography, Volume 14, pp. 398–403 (see p. 400), in 1934. In 1935 Ralph Barton Perry wrote in The Thought and Character of William James, v. 2, p. 436, that Peirce adopted "Santiago" as a name "presumably in honor of James".
Others followed with the same idea expressed less conditionally, for example Peter Skagestad in The Road of Inquiry, 1981, p. 234: "After James' death in 1910, Peirce began signing his own name Charles Santiago Sanders Peirce, thereby canonizing his old friend 'Santiago,' i.e. St. James"; John Deely in the editorial introduction, dated 1994, to the CP electronic edition: "Charles S. Peirce (the 'S' stands for 'Sanders' by Baptism and later for 'Santiago' as Charles' way of honoring William James)...."; James Hoopes in Community Denied, 1998, p. 30: "Peirce responded gracefully to James's aid and even adopted in old age the name "Santiago" (Saint James) as a tribute to his benefactor"; and Joseph Brent in Charles Sanders Peirce: A Life, 2nd ed. 1998, pp. 315–16, indicating the same connection, saying that Peirce took the name "Santiago" in May 1909, and adding an endnote: "MS 318".