Reply to Objection 2: Various answers have been made by certain writers to this objection which was raised by Julian the Apostate; for some, as Gregory of Nazianzum, say that the people mentioned by the two evangelists are the same, but under different names, as though they each had two. But this will not stand: because Matthew mentions one of David's sons---namely, Solomon; whereas Luke mentions another---namely, Nathan, who according to the history of the kings (2 Kgs. 5:14) were clearly brothers.
Wherefore others said that Matthew gave the true genealogy of Christ: while Luke gave the supposititious genealogy; hence he began: "Being (as it was supposed) the son of Joseph." For among the Jews there were some who believed that, on account of the crimes of the kings of Juda, Christ would be born of the family of David, not through the kings, but through some other line of private individuals.
Others again have supposed that Matthew gave the forefathers according to the flesh: whereas Luke gave these according to the spirit, that is, righteous men, who are called (Christ's) forefathers by likeness of virtue.
But an answer is given in the Qq. Vet. et Nov. Test. [*Part i, qu. lvi; part 2, qu. vi] to the effect that we are not to understand that Joseph is said by Luke to be the son of Heli: but that at the time of Christ, Heli and Joseph were differently descended from David. Hence Christ is said to have been supposed to be the son of Joseph, and also to have been the son of Heli as though (the Evangelist) were to say that Christ, from the fact that He was the son of Joseph, could be called the son of Heli and of all those who were descended from David; as the Apostle says (Rm. 9:5): "Of whom" (viz. the Jews) "is Christ according to the flesh."
Augustine again gives three solutions (De Qq. Evang. ii), saying: "There are three motives by one or other of which the evangelist was guided. For either one evangelist mentions Joseph's father of whom he was begotten; whilst the other gives either his maternal grandfather or some other of his later forefathers; or one was Joseph's natural father: the other is father by adoption. Or, according to the Jewish custom, one of those having died without children, a near relation of his married his wife, the son born of the latter union being reckoned as the son of the former": which is a kind of legal adoption, as Augustine himself says (De Consensu Evang. ii, Cf. Retract. ii).
This last motive is the truest: Jerome also gives it commenting on Mt. 1:16; and Eusebius of Caesarea in his Church history (I, vii), says that it is given by Africanus the historian. For these writers says that Mathan and Melchi, at different times, each begot a son of one and the same wife, named Estha. For Mathan, who traced his descent through Solomon, had married her first, and died, leaving one son, whose name was Jacob: and after his death, as the law did not forbid his widow to remarry, Melchi, who traced his descent through Mathan, being of the same tribe though not of the same family as Mathan, married his widow, who bore him a son, called Heli; so that Jacob and Heli were uterine brothers born to different fathers. Now one of these, Jacob, on his brother Heli dying without issue, married the latter's widow, according to the prescription of the law, of whom he had a son, Joseph, who by nature was his own son, but by law was accounted the son of Heli. Wherefore Matthew says "Jacob begot Joseph": whereas Luke, who was giving the legal genealogy, speaks of no one as begetting.
And although Damascene (De Fide Orth. iv) says that the Blessed Virgin Mary was connected with Joseph in as far as Heli was accounted as his father, for he says that she was descended from Melchi: yet must we also believe that she was in some way descended from Solomon through those patriarchs enumerated by Matthew, who is said to have set down Christ's genealogy according to the flesh; and all the more since Ambrose states that Christ was of the seed of Jechonias.