De Selby is the name of a fictitious Irish philosopher and scientist, originally invented by Flann O'Brien for his novel The Third Policeman. In this novel the character is known as "de Selby", with the latter capital D appearing in use in O'Brien's The Dalkey Archive. De Selby does not actually appear in the plot of the novel, but only in references and frequent footnotes, where his unorthodox theories and areas of research are, however tenuously, linked to the plot.[1] De Selby is heavily referenced in footnotes in this book, the longest of which takes up the bottom halves of eight pages and ends on a completely different note from the one on which it began.
De Selby has a host of critical analyzers – the narrator among them – many of whom have highly conflicting opinions of his esoteric thoughts. Although generally held in high regard by these people (many of whom hate each other), he is thought by many to have had regrettable lapses and is even called, by implication, a "nincompoop".
De Selby also appears in O'Brien's The Dalkey Archive, in which he develops a substance ("D.M.P.") capable of extracting all oxygen from an airtight enclosure, of disrupting the sequentiality of time, and of producing fine mature whiskey in a week.[2] De Selby vows to use the substance to destroy the world in the name of God.[2]
American author Robert Anton Wilson used de Selby in footnotes in his novel The Widow's Son. Wilson's de Selby is an expanded version of O'Brien's, and was involved in an unrequited romance with one of Gertrude Stein's lovers, a bitter academic feud spanning decades, and possibly intrigues involving the CIA. Also, Wilson replaces the concept of black air with that of teratological molecules, which are said to cause stunting of growth and are banished by electric light.