In contrast to ancient times, friendship is rarely discussed nowadays as a resource in moral education. Even within Aristotle-inspired character education, where it could naturally claim pride of place, its coverage is miniscule compared, say, to that of the emulation of moral exemplars. The aim of the present article is to retrieve friendship as a moral educational concept: to explain how moral educational goals define and sustain deep friendships, and how the thorny issue of when friendships should be terminated is best understood in terms of considerations as to whether they have exhausted their educational potential. By arguing that education is the "raison d'être" of deep friendship, Kristján Kristjánsson shows how friendship is developmentally constituted and, in its most complete form as "character friendship," educationally executed. There is no such thing as friendship "per se," but rather friendship at a certain developmental niveau (or level), with its specific developmental assets and liabilities: qualitatively differentiated according to its educational affordances. While operating within a broad Aristotelian framework, Kristjánsson devotes two sections to charting the moral educational liabilities that may dissipate even the most complete friendships, a topic mostly overlooked by Aristotle himself.