「道器關係」與「古今之辨」是「通經致用」的兩大關鍵問題。「經」之為「器」是明道之文，而道無古今，故此「通經」與「致用」不應該分離為二。通經即能致用。古今之隔不是問題。古經不必透過「創造性的現代詮釋」方能為今人所用。清代學者之所以認為「通經」在於「致用」，而現代學者之所以認為「通經」不必能「致用」，都是因為他們對「經」和「用」的想法有誤，要非受到魏晋以來「體用思考」的影響，不然就是受到現代西學中「歷史意識」的影響。本文借用戴震的經學思想對治前者，再借用Leo Strauss 對西方古今哲學之辨的見解來對治後者，以恢復「通經致用」之原有深義。

Dao/qi (principle/material, 道/器) relationship and distinction between ancient and modern are the two key issues of the proposition 'tongjing zhiyong' (to be proficient in classics benefits practical utilities, 通經致用). Classics as a kind of qi is in fact the literature illustrating what dao is, and dao is the same no matter in ancient or modern times, thus tongjing and zhiyong should not be separated into two. To be proficient in classics surely benefits practical utilities. Distance between ancient and modern is actually not a problem. The ancient classics need not so-called "creative modern interpretations" to be used by modern people. The reason why the Qing dynasty scholars thought tongjing aims at zhiyong, while modern scholars think tongjing does not necessarily leads to zhiyong, is that their ideas about these two phrases are wrong, since the former had been influenced by the ti/yong (form/content or theory/practice, 體/用) thinking passing down from the Wei and Jin dynasties, while the latter by modern Western thought of "historical consciousness." This paper borrows Dai Zhen ( 戴震)'s thought concerning Chinese Classics study to cope with the former, and Leo Strauss's view of distinction between Western ancient and modern philosophy in dealing with the latter, in order to restore the original deep meaning of the proposition 'tongjing zhiyong.'