As Bruno Snell says, “In Heraclitus the image of depth is designed to throw light on the outstanding trait of the soul and its realm: that it has its own dimension, that it is not extended in space.” Ever after Heraclitus depth became the direction, the quality, and the dimension of psyche. Our familiar term depth psychology says quite directly: to study soul, we must go deep, and when we go deep, soul becomes involved.
— James Hillman, The Dream and the Underworld, p. 25.