Perichoretic origin

Athanasius: “the Son is in the Father . . . because the whole being of the Son is proper to the Father’s ousia , as radiance from light and a stream from a fountain; so that whosoever sees the Son, sees what is proper to the Father and knows that the Son’s being, as from the Father, is the Father and is therefore in the Father. For the Father is in the Son, since the Son is what is from the Father and proper to him, as there is in the radiance the sun, and in the word the thought, and in the stream the fountain: for whoso thus contemplates the Son, contemplates what is proper to the Father’s ousia , and knows that the Father is in the Son.”

“As the thought is in the word”: Nicely said. Something we might expect from Hamann.