For its early history, the scholarly or Confucianist movement took as its primary texts the Five Classics -- the Book of Documents, the Book of Odes, the Book of Rites, the Book of Changes, the Spring and Autumn Annals, each of which is a kind of anthology of smaller works. By long tradition, they were thought to have been at least partly edited by Confucius himself. The Analects and the Mencius became widely read and respected entirely as commentaries on the Five Classics. The Five Classics came to be seen as rather difficult to understand on their own, and the demand for excellent commentary on them was considerable.
An epoch arrived in this commentary tradition with the great Zhu Xi, the greatest of all the Daoxue or Neo-Confucian scholars. In order to provide an easier, briefer introduction to the essential ideas, Zhu Xi recommended that students start with four works, which would come to be known as the Four Books: the Great Learning, the Analects, the Mencius, and the Doctrine of the Mean. Both the Great Learning and the Doctrine of the Mean were chapters from the Book of Rites that Zhu Xi held to be especially valuable for distilling the essential principles of Daoxue. He championed the idea that students should begin with these Four Books, and, while not universally accepted, this became the dominant expectation. (This was significant, in that it inevitably led to the Four Books displacing in practice -- although not in principle -- the Five Classics as the fundamental texts of Confucian thought.) Of the Four, Zhu Xi held that the Great Learning or Da Xue should be read first, as providing the general pattern of the Way, and specific steps according to which one should study. Students could then go on to the more difficult Analects to get the foundational principles, proceeding through the Mencius to get the development of these principles, and culminating in the Doctrine of the Mean to begin discovering more advanced topics. Zhu Xi argued that the Da Xue fell into two parts, a foundational text written by Confucius himself and a commentary on that text by Confucius's student Zengzi.
The Great Learning can be read online in James Legge's translation at the Chinese Text Project. I am beholden also to the excerpts and commentary of Daniel K. Gardner's The Four Books and to James Legge's notes on the work.
The text, while brief, turns out to hold hidden complications right from its first sentence. What does the 'great learning' mean? There are two possibilities, both of which can be found in Confucian commentators: it could mean extensive learning, in which the case the work is a summary of the scope of knowledge required for good governance, or it could mean learning for the mature or for adults, in which case the work summarizes the principles and structure of advanced study. A second textual issue arises in the very first sentence. It identifies three topics in which the Great Learning consists; the first is showing forth one's splendid virtue and the third is coming to rest in perfect goodness. The second, however, has two forms. In one form, it is loving the people. However, the Cheng brothers, who were a major influence on Zhu Xi, suggested that this was a corruption and it should read renewing the people. Because of Zhu Xi's importance, the latter reading has generally been taken as the most common. Under the traditional renewing interpretation, the great learning is a process: one starts with manifesting one's own virtue, which requires cultivating virtue in others, until this is complete.
That there is a process in view is confirmed by the next propositions of the text, which identify a series and insist on the importance of putting first things first. We need to know the end in view (where to rest), and given that we can set ourselves in proper order for considering what needs to be done to achieve it. This is shown by the example of antiquity. Wishing for everyone to manifest their inner virtue, they knew that they had to govern their states well; that requires harmony in households, which requires self-cultivation, which requires setting one's heart right, which requires sincere intent, which requires extension of knowledge, which requires investigation of principle, so this is where they begin. (Because the Da Xue gives investigation of principle pride of place as the first in the series, what exactly is meant by 'investigation of principle' will be one of the most important foundation-stones of the Neo-Confucian movement.) Zhu Xi notes that, despite the fact that this is structured as a series, movement from step to step can require considerable discipline and work.
All of this requires taking self-improvement to be essential; the right process of improvement begins with self-improvement, and without it nothing else can be done properly. What is more, this is something on which everyone should focus, regardless of their station in life.
This, then, is the classic or jing portion of the work. In the Liji or Book of Rites, there does not seem to be any sharp intended division between this portion and the rest, but the book does naturally fall into the parts when one looks at the content, which is almost certainly why Zhu Xi takes it to have the two parts. And, however we would interpret the Da Xue as a chapter in the Liji, as one of the Four Books the Da Xue has always been understood to have a classic portion and a commentary on it, so it makes sense to follow this tradition as we continue on.
to be continued