Plato’s Light and the Phenomenon of the Clearing  105

but many may not be aware that this line of thinking goes much further back. As early as 1926, Heidegger was sketching a reading of the allegory, which he would return to several times in later years. Specifically, to put these key elucidations in chronological perspective:

• 1926 lecture course, summer semester, at the University of Marburg, ‘The Basic Concepts of Ancient Philosophy.’²
• 1927 lecture course, summer semester, at the University of Marburg, ‘The Basic Problems of Phenomenology.’³
• 1931–2 lecture course, winter semester, at the University of Freiburg, ‘On the Essence of Truth’ (On Plato’s Cave Allegory and Theaetetus); not to be confused with the 1930 lecture ‘On the Essence of Truth,’ published in 1943.⁴
• 1933–4 lecture course, winter semester, at the University of Freiburg, ‘On the Essence of Truth’ (related to the earlier lecture course and not to the 1930 lecture).⁵
• 1940 essay ‘Plato’s Doctrine of Truth’ (published in 1942).⁶

The broad lines of his reading of Plato’s allegory are generally well known, so what I wish to focus on is his understanding of the character and role of light. Already in his 1926 lecture course, Heidegger roughly establishes his basic reading: Plato glimpses in his thinking that the Idea of the Good is ‘beyond’ (epekeina) beings and even being(ness) in the sense that it ‘enables’ or ‘makes possible’ all beings in their beingness (their full ‘appearance’ or ‘look,’ what Plato called the eidos or idea and what later came to be understood as the enduring presence or ‘essence’ of a thing, the core concern of metaphysics). For Heidegger, Plato’s Idea of the Good is no ‘it’ at all, no something, no essence or value; rather, the Idea of the Good is to be understood as the (temporal) ‘enabling’ (ermöglichend) of all beings in their beingness. As he excitedly expresses his insight in the lecture course, the Idea of the Good is ‘the most originary possibility! Originarily enabling everything.’⁷ With respect to the imagery of the allegory, he correlates the Idea of the Good with the ‘light itself,’ the ‘illumination’ that makes possible ‘anything at all to be seen.’ This purely enabling ‘light,’ which he identified as the ‘sun’ according to Hermann Mörchen’s student lecture notes, is not the light belonging to illumined entities, but rather the source of all light. This light, the light-source itself, makes possible all lighted beings.⁸

A year later in his 1927 summer lecture course, he returned to a reading