A.D. Nuttall (2003) answers:

The word, I think, connotes a quality of completeness: at the lowest level, complete literacy (never a colon where a comma should be); complete, though not redundant documentation; complete accuracy even with reference to matters not crucial to the main argument, and, together with all this, a sense that the writer’s knowledge of material at the fringe of the thesis is so sound as his or her knowledge of the core material. This seems to me to be the essence of the matter—that although there may be a strong central thesis which rightly absorbs most of the energies available, the writer nevertheless maintains a broad front of total accuracy, a sort of democracy of fact, in which no atom of truth shall be slighted, however humble in relation to the main theme. (emphasis original, p. 191)