The Core Objection: Joseph as a Legal Rather Than Biological Father
The earliest Christian writers were well aware of this objection. In fact, Thomas Aquinas’s Summa Theologica opens Article 2 on this very question — “Whether Christ took flesh of the seed of David?” — with the objection that since Matthew traces Jesus’s genealogy to Joseph, and Joseph was not Jesus’s biological father, “it seems that Christ was not descended from David” .
The Manichaean heretic Faustus pressed this argument sharply around the 4th century, preserved in Augustine’s Contra Faustum: “the son said to have been born of Mary cannot properly be called the son of David, unless it is ascertained that he was begotten by Joseph. You say he was not, and therefore you must allow him not to have been the son of David” . Faustus went further, arguing that Mary herself appeared to belong to the priestly tribe of Levi (her father Joachim being a priest), not the royal tribe of Judah, making it even harder to trace Davidic descent through her .
The Two-Pronged Christian Response
1. Mary Was Herself of David’s Line
The Church Fathers did not simply rely on Joseph. The Angel Gabriel in Luke 1:27 refers to Joseph as being “of the house and lineage of David” — but John Chrysostom points out that this also demonstrates Mary was of the same stock, because Jewish law prohibited marrying outside one’s tribe . Augustine insists: “We believe that Mary, as well as Joseph, was of the family of David, because we believe the Scriptures, which assert both that Christ was of the seed of David after the flesh, and that His mother was the Virgin Mary” .
John of Damascus (8th century) explicitly states Mary “sprang at the pre-determined time from the root of David, according to the promises that were made to him” . He notes the evangelists’ silence on Mary’s genealogy was simply a matter of custom: “it was not the custom of the Hebrews nor of the divine Scripture to give genealogies of women” .
2. The Levirate Marriage Solution (Africanus’s Account)
The most sophisticated answer comes from Julius Africanus (c. 160–240 AD), preserved by Eusebius in his Church History . It resolves the apparent discrepancy between Matthew’s and Luke’s genealogies and explains how Joseph could be the legal conduit for Davidic succession even without biological fatherhood.
The tradition, as Africanus reports it, goes like this:
- Matthan (descended from David through Solomon) married a woman named Estha and fathered Jacob.
- After Matthan’s death, Melchi (descended from David through Nathan) married the same widow, Estha, and fathered Heli.
- Jacob and Heli were thus uterine half-brothers — same mother, different fathers.
- Heli died childless. Jacob, under the levirate law (Deuteronomy 25:5), married Heli’s widow and fathered Joseph.
- Joseph was therefore Jacob’s son by nature (biological) but Heli’s son by law (levirate succession) .
This is why Matthew says “Jacob begat Joseph” (tracing the natural line through Solomon) while Luke says Joseph was “the son of Heli” (tracing the legal line through Nathan). Augustine and Jerome both endorse this explanation .
How This Answers the Question
The levirate marriage tradition means Joseph carried Davidic descent both biologically and legally:
- Biologically, Joseph was the natural son of Jacob, who descended from David through Solomon (Matthew’s genealogy).
- Legally, Joseph was the son of Heli by levirate succession, descending from David through Nathan (Luke’s genealogy).
- Under Jewish law, the son born to a levirate marriage (Joseph) was the legal heir of the deceased brother (Heli).
- When Joseph married Mary, his legal status as a son of David transferred to Jesus through adoption (or, in Roman legal terms, through the father’s head of household).
- Additionally, if Mary was also of David’s line — which the Fathers argue she must have been, since marriage across tribes was forbidden — then Jesus had Davidic blood from both sides.
As Augustine puts it: the evangelists could not properly say Heli “begat” Joseph (since he was not the biological father), which is why Luke uses the phrase “who was the son of Heli” — allowing for adoption or levirate succession .
The Jechoniah Problem
One further wrinkle: Matthew’s genealogy passes through Jechoniah (Jehoiachin), of whom Jeremiah 22:30 says “Write this man barren… for there shall not be a man of his seed that shall sit upon the throne of David.” Aquinas addresses this: Ambrose held that the prophecy did not deny a posterity to Jechoniah — it denied that any would reign with worldly honor, which Christ’s kingdom was not . Irenaeus (2nd century) actually used this curse against those who claimed Jesus was Joseph’s biological son, arguing they “cause themselves to be disinherited from the kingdom” by tying Jesus to the cursed line .
