The present study aims at a complex investigation into the meaning and the text of the Fourth Letter of Pseudo-Dionysius. For this endeavour it uses methods pertaining to the history of philosophy, the history of theology, philology, text criticism, the study of text transmission, and Quellenforschung. The result is a reinterpretation of the text and meaning of the Fourth Letter and, per consequent, of the stance of Pseudo-Dionysius in the contemporary Christological debates. Thus, besides providing a new edition of the Greek text of the Fourth Letter, it also reconstructs the essential elements of Dionysius’ Christological doctrine, showing that it is an artful blend composed of the Neoplatonist exegesis of the third and fourth hypotheses of Plato’s Parmenides, of the Origenist theory of the Incarnation elaborated by Evagrius of Pontus, and of the Christological doctrine of Theodore of Mopsuestia. It also shows the importance of the indirect text tradition of the Dionysian Corpus for a critical study of its direct text transmission.