All is light

Strangely, Paul says in Ephesians 5:13 that “everything that becomes visible is light.” Whatever could that mean?

Hamann thought he knew: “Imagery comprises the entire realm of human knowledge and happiness. The first explosion of creation, and the first impression of its historian; the first manifestation and the first enjoyment of nature unite in the word: ‘Let there be light!’ with this begins the perception of the presence of things.” And he footnotes Ephesians 5:13 in support.