Professor Mok received his BA and MPhil degrees from the University of Hong Kong and D.Phil. degree from the University of Oxford, UK. An historian of Chinese art, he taught at the University of Hong Kong before joining the Department of Fine Arts at CUHK in 1989. Professor Mok teaches courses in the history of Chinese painting and calligraphy and methodology in art studies. He was Head of Division of Fine Arts in 2002–2008, and is now Chairman and Professor of the Department, as well as Expert Adviser (Museum) to the Leisure and Cultural Services Department. His research focuses on post-Tang calligraphy and Hong Kong calligraphy. In recent years, he has completed three research projects on Hong Kong calligraphy, Chunhua Ge Tie, and calligraphy of private secretariats in the Qianlong and Jiaqing periods. In addition to publishing academic papers, Professor Mok has also edited The Bei Shan Tang Legacy: Chinese Calligraphy (2015), Chronology of Hong Kong Calligraphy 1901–1950 (2009), Shuhai Guanlan (1998 & 2008), Double Beauty II (2007), Xuedao Yangchen (2003), Bimo Lunbian (2002), and Hong Kong Visual Arts Yearbook (1999, 2000, 2003, 2004, 2005, 2006).

During the luncheon, Professor Mok began by introducing several calligraphic works by Deng Erya housed in the Art Museum and pointed out that Deng was not only a famous calligrapher and seal carver but also an expert of Chinese philology. As such, in order to better understand the uniqueness of Deng's calligraphy, one has to look into how his interest and knowledge of philology has played a role. Professor Mok said that Deng Erya's surviving work of philology, entitled The Origin of Chinese Characters (《文字源流》), is a very important reference in this context. This 21-volume handwritten manuscript, now collected in the Hong Kong Museum of Art, demonstrates the calligrapher's knowledgeability about Chinese philology and his research findings of ancient Chinese characters, which are readily reflected in his calligraphy. Although never published probably because of the difficulties involved in typesetting the unusual forms of ancient characters and in transcribing the often illegible handwritings, the work was made a handy reference in the luncheon presentation.

Professor Mok pointed that Chinese calligraphers always learn from the past, and it is therefore important to know how Deng Erya saw the tradition. When discussing the seal script of the Qing dynasty, Deng gave particular credit to Deng Shiru, Wu Dacheng and Yi Bingshou. Deng Shiru's seal script was ranked under the Divine class as it was perfect in both brushwork and character structure. As for Wu and Yi, Deng praised the former for being able to adopt the brush method of bronze script and the latter for his success in integrating the clerical script with seal script. In addition to these three masters, Deng also highly regarded Huang Shiling, whose calligraphy could be stylistically traced back to the ancient past even though he did not have the opportunity to study oracle-bone inscriptions. Although all were unique in their own right, these four masters had one thing in common, i.e. classic elegance and neatness in style, of which Deng Erya was very much in favour. In fact, such an artistic taste explained why Deng frowned on some Qing calligraphers' practice of burning or cutting the tip of the brush for producing perfectly even strokes in seal script, or why he dismissed the Ming calligrapher Zhao Yiguang's cursive-seal calligraphy for its excessive lack of restraint that bordered on vulgarity. Professor Mok particularly pointed out that Chen Li, who stated in his Discussions on Seal Carving (《摹印述》) that "elegance and neatness are of paramount importance for the seal script", probably had a great bearing on Deng, who claimed himself to be his third-generation student and to have been reading his Discussions on Seal Carving since childhood.

Deng's extant calligraphies included a rather special type of seal-script calligraphy that displayed "elegance and neatness" (雅正) to the extreme. Named by Deng as "symmetrical seal script" (反正篆), this type of calligraphy is unique as the form of each character in any given piece remains unchanged whether viewed from the front or the back. As suggested in his Origin of Written Words, the time-consuming composition of a couplet with symmetrical characters was possibly invented by Wu Zi of the Qing dynasty. Although the Art Museum did not have examples of this type in its collection, Professor Mok said that there were at least seven surviving couplets by Deng, one of which was in the collection of the Hong Kong Museum of Art. He also added that Deng's "symmetrical seal script" was once criticized to be overly symmetrical at the expense of artistic beauty but such negativity in fact stemmed from an oversight that the calligrapher was driven by his great interest in and profound knowledge of Chinese ancient characters.

In addition to "elegance and neatness", which were to be the essential qualities, Deng Erya further advocated naturalness. To enliven the small seal script and to in turn achieve naturalness artistically, Deng made use of the large seal script, which was relatively awkward in form, as fairly commented in the newspaper Wah Kiu Yat Po (28 October 1954), noted Professor Mok.

In The Origin of Chinese Characters, Deng pointed out that brush method and philology were of equal importance in calligraphy in the very beginning but calligraphers since the Jin and Tang dynasties gradually focused on only the former while ignoring the latter. Professor Mok pointed out that since Deng Erya was himself philologist, his great interest and rich knowledge of ancient Chinese characters featured rather prominently in his art of calligraphy. He cited Deng's Thousand-character Essay in seal script as an illustration. The original essay contained the character "ming" (銘) with the standard "metal" radical but Deng was prevented by taboo from using it since it happened to be his grandfather's name. To resolve the problem and as explained in his own inscription to the calligraphic work in question, he adopted the variant form (詺) with the "speech" radical from a Tang stele and justified himself by quoting from Chen Li's Discussions on Seal Carving that variants left out in the lexicon Dissecting Characters (《說文解字》) were acceptable so long as they appeared in stele inscriptions. Despite his accomplishment, Deng admitted in the same inscription that philology was a demanding discipline that required meticulous research. Indeed, Deng's extant calligraphies fully demonstrate that every single character that he wrote was carefully chosen and was philologically valid.

Professor Mok further elaborated on Deng Erya's application of philological scholarship in calligraphy with reference to four pieces of couplets in seal script. In these works, characters in the small seal-script form are juxtaposed with those in archaic form, in bronze inscriptions and even in oracle-bone inscriptions. In using of these characters, many of which were non-standard in form and hence were regarded as "rare characters" (僻字), the calligrapher did not intend to show off by being different. It was more a reflection of how his learning of philology was given expression in calligraphy.

Deng Erya's interest in ancient characters could also be found in his use of "variant characters" (別字) in regular-script calligraphy, as best demonstrated by his scrolls of Heart Sutra (《心經》). Although the one housed in the Art Museum was not an example in this regard, there were at least two scrolls known to have been written with "variant characters", one being in the Dongguan Municipal Museum collection and the other produced as a gift for Deng's wife. The original text of Heart Sutra contains a number of recurrent characters such as "wu" (無, 20 times) and "bu" (不, 9 times). In the two scrolls in question, Deng widely made use of "variant characters" so that none of the repeated characters looked the same, resulting in a fascinating visual effect. The Art Museum is honoured to have received the generous donation of a volume of Deng's handwritten manuscript of variant characters for Heart Sutra from Deng's fourth son Mr. Deng Zufeng. In the volume, 26 different forms are listed for the character "wu" and 16 for "bu", all of which are "variant characters" that Deng identified from Six Dynasties stelae. Deng must have gone to great lengths to collect unusual characters for his regular-script calligraphy, just as he did for his seal script. Yet, no matter how "strange" his calligraphy may look, his juggling of character forms was always squarely based on his profound knowledge of philology.

In his concluding remark, Professor Mok reiterated that according to Deng Erya, calligraphy was an art that displayed brush skills and embodied philological learning. In this light, his knowledge of ancient characters must not be overlooked or ignored if his calligraphy was to be fully understood. The fashion in which the calligrapher used "rare characters" and "variant characters", as highlighted in the presentation, may very well served to illustrate how important philology was in his calligraphy.