Wenzilun 文字論 "On Chinese characters" is an essay on Chinese characters and calligraphy written during the mid-Tang period 唐 (618-907) by Zhang Huaiguan 張懷瓘 (mid-8th cent.), who is more famous for his book Shuduan 書斷.
Zhang first defines the words wen 文, zi 字, and shu 書. The expression wen (simple characters) was the "ancestor", the basic appearance, pattern imitating nature (wenli 文理), and model of characters. From these patterns (文=紋), the many "offspring" (zi 孳) zi 字 (compound characters) emerged. The expression shu 書 was used to denote the characters of texts written on bamboo slips and silk. While it was necessary to use many wen characters to express a meaning, shu-type characters were self-explanatory (yi zi yi jian qi xin 一字已見其心).
The text of the Wenzilun is written in the form of a dialogue. It explains that a true master of calligraphy only regarded the "spirit and colour" (shencai 神彩) of a character and not its shape. At first glance, it may seem enigmatic, but as one observes it more, its value becomes increasingly apparent. Even after a calligraphic work is completed and set aside, its impact remains if it engages and moves the observer emotionally (xin zhui mu ji 心追目極). This enduring fascination and deep appreciation define the true subtlety of the art (shi wei miao yi 是爲妙矣).
The text is quoted in the book Shuyuan jinghua 書苑菁華 and included in the series Meishu congshu 美術叢書 and Lidai shufa lunwen xuan 歷代書法論文選.