This paper focuses on Plato’s “Form of the Good,” or “the Good,” with an interest in Plato’s riddle that “the Good is the One.” Unlike the traditional approach to explaining the Good in the Republic as “rational order” or a unity of Forms, this paper argues that the Good is the unique transcendent principle, like the apex of a hierarchy, but does not encompass the whole structure. According to its Ontological position, its multiple facets (functions) include the Ontological foundation of uniting “to be” and “ought to be,” the ultimate source of knowledge, and the Ideal goal of uniting the common good and individual goods. The practical dimension of the Good is highlighted in exploring the lifelong study of the Philosopher-Kings and their political personality. It is also pointed out that “sudden enlightenment” plays an important role in their path toward the Good. Finally, this paper proposes that the Good should be the a priori beginning of education and the end of the practice of virtues in the community.