Anne Carson, Eros the Bittersweet

“But the ruse of the triangle is not a trivial mental maneuver. We
see in it the radical constitution of desire. For, where eros is lack,
its activation calls for three structural components—lover, beloved
and that which comes between them. They are three points
of transformation on a circuit of possible relationship, electrified
by desire so that they touch not touching. Conjoined they are
held apart.”