You should generally use quotation marks if you repeat a quotation from the same source, but you may omit quotation marks when referring back to a concept or method (e.g., distant reading) mentioned in the source:
Moretti takes issue with this tendency to regard literature at any level as “a world” complete and classifiable rather than one in production and changing unevenly. Ironically, coming from someone obviously given to spatial diagrams of literary phenomena, “distant reading” adheres to the principle that “spatial proximity never turns into functional interaction” (14). Moretti won’t let us construe the distance implied by distant reading in opposition to the closeness and polysemy of literary language.
Moretti, Franco. Distant Reading. Verso, 2013.
Note: The example is adapted from Nancy Armstrong and Warren Montag’s “‘The Figure in the Carpet’” (PMLA, vol. 132, no. 3., May 2017, pp. 613–19).
Published 2 November 2018