許慎
Central to Xu Shen's thought is the contrast between "wen" (文 patterns) and "zi" (字 characters), indeed these contrasting categories of graphs receive separate mention in the work's title. Even today, there is disagreement over the exact definitions of the two terms. The Song dynasty scholar Zheng Qiao () first presented the interpretation that "wen" and "zi" are the difference between non-compound and compound characters. More recently, other scholars, such as Françoise Bottéro (2002), have argued that the addition of a specifically phonetic element (and thus not simply compounding) marks the principal difference between "wen" and "zi". From this original binary contrast, Xu Shen formally delineated for the first time the six categories () of Chinese characters.