Where does "there is a sequence of knowledge and a specialization in art" come from? Who said that? How to translate?

The original sentence: There is a sequence of teaching and learning, and there is specialization in the technical field;

source: Tang Han Yu Shi Shuo;

explanation: hearing: knowing the truth: reasoning: skill industry: study

specialization: specialized research

translation: hearing the truth has a priority (early and late), and everyone has his own expertise in technical studies/knowing the truth first, and his skills and studies have their own special research;

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