The Wallace Collection consists primarily of miscellaneous letters written by and to the English naturalist, Alfred Russel Wallace, primarily during the period 1880-1913. An innovative thinker, Wallace's correspondence reflects his strong commitment to evolutionism, to his version of "Darwinism," and to his adopted Spiritualism.

Although a significant portion of the collection is comprised of relatively routine correspondence, several letters provide insight into Wallace's perspective on evolutionary change between the 1870s and early 1900s. Among the best of these letters is Wallace's response to the claim of the otherwise unidentified R. Murray (May 2, 1890) that a cat with a "mutilated" tail had produced entirely tailless offspring. Wallace toes a delicate line between remaining open to the possibility of the inheritance of acquired characteristics and simply rejecting that possibility as too difficult to verify. The correspondence also suggests something of the degree to which Wallace was integrated into contemporary scientific networks, particularly a letter to Samuel Scudder (April 12,. 1876) requesting information on tropical entomology and botany; a letter from Alphonse de Candolle, and letters from members of Darwin's circle, including Flower and Hooker. Other letters from Tyndall and Spencer are more social in nature.

Throughout his life, Wallace considered himself a loyal, though heterodox Darwinian, concerned as much with the why of evolutionary change as the how (see letter to W. J. Farmer, Dec. 3, 1908). One letter includes a particular direct assessment of the work of Darwin and his alleged reticence in publishing the Origin (August 6, 1908). A writer in the New York Evening Post, he wrote,

Spiritualism was a major point of intellectual involvement for Wallace during the last forty years of his life, and several letters in the collection sketch out his interests. That he was not always successful in convincing his peers of the truth of Spiritualism need not be noted. Three letters from the skeptical philosopher and novelist, Samuel Butler (May 22, 24, and 27, 1879), are particularly noteworthy for revealing his colleagues' reaction to Wallace's beliefs, although Wallace had better success with his fellow believer, Epes Sargent (Dec. 13, 1880) and with Archdeacon Colley (Feb. 26, 1907). With Colley, Wallace discussed the reality of materialization séances and rejecting the illusions of the magician and anti-Spiritualist, John Nevil Maskelyne.

Wallace also retained his "radical," Socialist political views until the end of his life. Although the collection offers little to flesh out Wallace's politics, several letters provide brief glimpses, particularly the two letters to the Socialist animal rights advocate, Henry Stephens Salt (Sept. 26, 1897 and Jan. 11, 1898), and a nice letter to W. R. Hughes (May 31, 1908) regarding Wallace's article in the Socialist Review. Most revealing, perhaps, is Wallace's list (Jan. 14, 1907) of the "ten chief humanitarians of the nineteenth century": Robert Owen, Leo Tolstoy, Edward Bellamy, Robert Blatchford, Elizabeth Fry, John Ruskin, Shelley, Walt Whitman, William Watson, and Edwin Markham.