The question of whether "The Canterbury Tales" is a finished work has not been answered to date. There are 84 manuscripts and four incunabula (printed before 1500) editions of the work, dating from the late medieval and early Renaissance periods, more than for any other vernacular English literary text with the exception of "The Prick of Conscience". This is taken as evidence of the "Tales"' popularity during the century after Chaucer's death. Fifty-five of these manuscripts are thought to have been originally complete, while 28 are so fragmentary that it is difficult to ascertain whether they were copied individually or as part of a set. The "Tales" vary in both minor and major ways from manuscript to manuscript; many of the minor variations are due to copyists' errors, while it is suggested that in other cases Chaucer both added to his work and revised it as it was being copied and possibly as it was being distributed. Determining the text of the work is complicated by the question of the narrator's voice which Chaucer made part of his literary structure.