It is necessary to begin the story-line of our enquiry somewhere. And though it is always possible to take the story back historically beyond a chosen starting point, the primary interest of this study is systematic and conceptual, rather than historical. When I say, therefore, that a source for the Western Christian employment of the metaphors of darkness and light and of ascent and descent may be found in the impact of converging Greek and Hebraic influences on Western Christian thought, I have primarily in mind a deductive possibility, designed to shed light on an historical claim. I maintain, that is to say, that you could extract the main linguistic building blocks of the Western Christian tradition from the quarry of this convergence, and, even more particularly, that you could extract those building blocks from two stories, each foundational in the intellectual and religious cultures of its respective tradition: the ‘Allegory of the Cave’ in Book 7 of Plato's Republic, and the story in Exodus of Moses' encounter with Yahweh on Mount Sinai. You could do this: that is to say, with those two stories as premisses, you could satisfactorily derive much of the distinctiveness of the language of the Western Christian mystical tradition as conclusion.

Nevertheless, it is perfectly reasonable to go beyond a point merely in explanatory logic. There is little doubt that, whether it was the Greek cast of mind picking up the religious significance of Exodus in Platonic terms, or an Hebraic mind which seized upon the philosophical opportunities to be explored in Plato, this convergence did happen and was consciously acknowledged to have happened by theologians both of Greek and Latin traditions.