Some recent work in humanistic (Robbins, 2008) and positive (Martin, 2007) psychology speaks of a renewed focus in the discipline on values, happiness, and notions of the "good life." This renaissance is based on a philosophical concept of goodness that merits further exploration. This article elucidates an ancient concept of "the Good" offered by Plato and Aristotle that undergirds the humanistic (and positive) traditions. These thinkers speak of this Good as the fulfillment of all desire and spell it with a capital "G" to distinguish it from the many other kinds of good that fill our world. This classical understanding of the Good is often eclipsed by modern tendencies to see it as something to fear due to its tendency to cause argument and division. Given humanistic psychology's historical roots in this classical philosophical tradition, a firm conceptual grasp of the Good is vital for understanding many of humanistic psychology's own core ideas, such as inner nature, flourishing, freedom, and culture. I offer a set of propositions at the end of the article that delineate a humanistic psychology that is rooted in the Good.