Plato’s Light and the Phenomenon of the Clearing 107
The light [das Licht] that constitutes this lightedness [Gelichtetheit] of Dasein is not something ontically present-at-hand as a power or source for a radiant brightness occurring in this being on occasion ... This lightedness first makes possible all illuminating or illumining, every perception, ‘seeing,’ or having of something. We understand the light [das Licht] of this lightedness only if we are not seeking some power implanted in us and present-at-hand. (my emphasis)16
Though he does not mention Plato’s allegory explicitly in this passage, it is clearly in the background of his thinking. The ‘light’ that he speaks of that metaphorically characterizes Dasein’s always-already temporally disclosive character (logos) is perfectly parallel to the ‘sun’ of the allegory, the light-source, that enables or makes possible all that is lighted and directly visible to the eye. Consequently, this part of §69 of Being and Time really cannot be fully understood until we refer it to Heidegger’s reading of the role of light in his Plato elucidations of 1926 and 1927. In these texts, we find him appropriating Plato’s metaphor of light in order to articulate his primary concern with that which enables the truth of all beings in their beingness – the enabling, which, on his reading, Plato had glimpsed as ‘beyond being[ness].’
Heidegger first fully developed and unfolded his reading of the allegory in his 1931–2 winter lecture course ‘On the Essence of Truth.’ This lecture course is not to be confused with the widely known lecture of the same title that he first delivered in 1930 (and later published in 1943), nor with the lecture course, again of the same title, from the winter semester of 1933–4, which was largely a restatement of the themes of the earlier lecture course. His lengthy and painstakingly careful elucidation of the allegory takes up all of Part I of the 1931–2 lecture course. There are many remarkable insights and observations along the way, but let us keep our focus on his reading of the role of light, which, in fact, is central to the entire reading. Early on, he makes this important distinction:
Already here, and for the understanding of the whole allegory (of all following stages), it is necessary to make note of the difference between pur, fire (the light-source [Lichtquelle]), and phos, brightness (to which there corresponds in the Latin: lux and lumen).17
Though he does not remain perfectly consistent in employing these terms in precisely this way as he proceeds, he nonetheless maintains