The present contribution argues that the study of the interaction between philosophy and epistolography in Byzantium faces a number of methodological challenges. First, the study of Byzantine philosophical literature, including philosophical epistolography, depends on one’s definition of philosophy in respect to its cultural, intellectual, social, and disciplinary context in Byzantium. Second, essential for the examination of philosophical epistolography in Byzantium is the critical assessment of the category of philosophical letter and its relevance to the Byzantine material. Finally, the author argues that one possible venue for examining philosophical epistolography in Byzantium is the discussion of literary friendship and theories of friendship as developed in friendship letters. To illustrate the theoretical approach it proposes, this contribution offers a case study of two letters written by Nikephoros Gregoras (d. c.1360).