The essence of the Buddha's teaching can be summed up in two principles:
the Four Noble Truths and the Noble Eightfold Path. The first covers
the side of doctrine, and the primary response it elicits is
understanding; the second covers the side of discipline, in the broadest
sense of that word, and the primary response it calls for is practice.
In the structure of the teaching these two principles lock together into
an indivisible unity called the dhamma-vinaya, the
doctrine-and-discipline, or, in brief, the Dhamma. The internal unity of
the Dhamma is guaranteed by the fact that the last of the Four Noble
Truths, the truth of the way, is the Noble Eightfold Path, while the
first factor of the Noble Eightfold Path, right view, is the
understanding of the Four Noble Truths. Thus the two principles
penetrate and include one another, the formula of the Four Noble Truths
containing the Eightfold Path and the Noble Eightfold Path containing
the Four Truths.