《中庸》原為《禮記》一篇，獨立後成為理學重要文獻。不過，《中庸》首章不見「中庸」一詞，對「中庸」討論的篇章既不多，也欠明確的定義。因此，部分觀點認為《中庸》可能原為兩部分拼合而成，前後主題分別為「中庸」與「誠明」。甚至，「中庸」的概念應回歸「禮以制中」的禮學意義。相對地，朱熹等理學家則相信《中庸》結構嚴謹，並以首章為理解全篇的綱領。朱熹以當厚則厚、當薄則薄為中，因此，所謂「中庸」的根本含義其實是「權衡輕重」、「恰當合宜」。至於權衡用中的判準，則在依乎天理；而天理流行，真實無妄，即為誠。如此，全書「中庸」與「誠明」前後主題便能貫串為一整體。不過，依此理解，《中庸》整體性最根本的概念，其實是天理。且如此一來，「中庸」便不是個明確的概念，必天理渾然，乃能得中取中。這正也是《中庸》在理學脈絡下，與禮學意義的差異。

As originally one article of Liji, Zhongyong came to be an important document of Neo-confucianism after extracted. However, the concept of mean is not found in the first chapter, and discussions about the concept are not sufficient, even without clarified identification. Therefore, some scholars think that Zhongyong is assembled by two parts, and the concept of mean should be understood back to the ritual study. To the contrary, ZhuXi believed that Zhongyong was an integrated work with the first chapter as the guiding principle. In ZhuXi’s opinion, the principle of mean means to make appropriate, and the criterion of appropriateness is heavenly principles. The pure heavenly principle means Cheng. Thus, the whole book is integrated as one. In the way of comprehension, the heavenly principle is the most fundamental concept in stead of Zhongyong. Consequently, Zhongyong is not a clear concept until heavenly principle get purely presented.