As a professor of history at Johns Hopkins University from 1910 to 1939, Lovejoy founded, and presided for decades over, the university's History of Ideas Club, which was a meeting-place for many of the early-to-mid-20th century's foremost intellectual and social historians and literary critics. He also founded the Journal of the History of Ideas. Lovejoy's "history of ideas" was notable for its insistent focus on "unit-ideas," single concepts (often expressed in single words) which it traced as they were expressed in different combinations through time.
Reference
Arthur O. Lovejoy, The Great Chain of Being: A Study of the History of an Idea, (Cambridge: Harvard University Press, 1936, 1961, 1970).
External links
the online Dictionary of the History of Ideas article on "the Chain of Being" (http://etext.lib.virginia.edu/cgi-local/DHI/dhi.cgi?id=dv1-45) credits Lovejoy