Cave of the heart

All metaphysics including its opponent positivism speaks the language of Plato. The basic word of its thinking, that is, of his presentation of the Being of beings, is eidos, idea: the outward appearance in which beings as such show themselves. Outward appearance, however, is a manner of presence. No outward appearance without light -- Plato already knew this. But there is no light and no brightness without the opening. Even darkness needs it. How else could we happen into darkness and wander through it? - Martin Heidegger, On Time And Being

Leonardo da Vinci anatomical drawings