The sixteenth edition of the Manual (1026 pages, 37 comma rules) carried these principles still farther away from that “subjective element”: the preface announced that the book would “recommend a single rule for a given stylistic matter rather than presenting multiple options.” Exceptions were eliminated where possible. This was what the Manual’s users wanted, though it’s unclear whether firmer and more numerous rules really reduced uncertainty, if The Chicago Manual of Style’s popular “Chicago Style Q&A” web page is any indication.
