In the stained glass God the Father by Józef Mehoffer in the chancel of the cathedral in Freiburg (Switzerland), the inscription ‘Je suis celui qui sui’ specifies the subject of the representation. The text also co-creates the phenomenon of epiphany: the inscription and the Divine countenance either emerge from among an effusion of colours, reminiscent of fire and precious stones from the vision of Ezekiel and Daniel, or else merge with the decorative mosaic of geometrical shapes building up the entire composition. The use of the pronoun ‘I’ personalizes the relation: viewer–work of art, placing every viewer who looks at the window in the position of someone who listens to the words Yahweh had spoken on Mount Horeb. And finally, the execution of the inscription in the stained-glass technique brings out its visual aspect. A painter’s work makes writing visible.