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.