Substantial act and esse secundarium: A critique of Lonergan's 'Ontological and Psychological Constitution of Christ'

Lonergan proposes in his Ontological and Psychological Constitution of Christ that in Christ there are two substantial acts, one the divine act of the Word, the other a created supernatural act actuating the human nature of Christ. He derives this teaching from a reading of Aquinas' Quaestio Disputata de Unione Verbi Incarnati, where Aquinas speaks of a secondary esse in Christ, besides the primary divine esse. Lonergan does not properly appropriate Thomistic metaphysics, since for Aquinas a single hypostasis can only have one substantial esse. He also reduces the Incarnation to a relation, thereby making it an accidental rather than substantial union. He also introduces something which is neither human (since the secondary act is supernatural) nor divine (since it is created) into Christ. Rather than reading the secondary esse in terms of substantial act, a more fruitful approach is to read it in terms of Aquinas' theology of kenosis.