The "Christ copied from pagan myths" thesis is called the copycat or Zeitgeist theory, after the 2007 documentary that popularized it. The claim is that early Christians cobbled Jesus together from pieces of existing mystery religions — a born-of-a-virgin, dying-and-rising savior god whose myths predate Christianity and explain it away. The problem is that the claim is almost entirely false. The alleged parallels either do not exist in the original sources, or they postdate Christianity, or they describe something substantially different from what the Gospels say. Let's take them one at a time.
Horus of Egypt
Claim: Born of a virgin on December 25, had twelve disciples, was baptized at age 30, performed miracles, was crucified, buried three days, and resurrected.
Actual Horus myth (from the Pyramid Texts, c. 2400 BC, and Plutarch, Isis and Osiris): Horus was conceived when the goddess Isis magically assembled the dismembered body of her dead husband Osiris (after 13 of 14 pieces were recovered — the 14th was eaten by fish — so Isis fashioned a replacement phallus of gold) and conceived Horus from the reconstructed corpse. That is not a virgin birth. Horus was not born on December 25 (the Egyptian sources give several dates, none matching). He had no twelve disciples. He was not baptized. He was not crucified. He did not rise from the dead. He fought a cosmic battle with Set, ruled Egypt, and eventually became the falcon-headed god of the sky. The "parallels" are invented.
Mithras
Claim: Born of a virgin on December 25, had twelve disciples, was called "the Way, the Truth, and the Light," was crucified, buried three days, resurrected.
Actual Mithras cult (reconstructed from inscriptions and iconography; the cult was secretive and left few texts): Mithras was born fully grown from a rock on a date no surviving source specifies. He had no disciples in the biblical sense. He was never crucified. He was not buried. He did not rise from the dead. His central myth is the slaying of a primordial bull, whose blood generated life. The cult — a Roman mystery religion for men, popular in the military — postdates Christianity as we know it; Mithraism in its Roman form emerges in the late first and early second centuries AD, after the Gospels were already written. Whatever borrowing occurred (and some may have), it ran from Christianity to Mithraism, not the other way around.
Dionysus
Claim: Born of a virgin, turned water into wine, crucified, rose from the dead.
Actual Dionysus myth: He was the son of Zeus, who seduced a mortal woman named Semele (not a virgin conception — Zeus was famously not a gentleman in these stories). He was stitched into Zeus' thigh after his mother was incinerated. He grew up to become the god of wine and ecstatic revelry. In one version he was torn apart by Titans and reassembled — but this is a dismemberment-and-restoration myth, not a death-burial-resurrection in any form that maps onto the Gospels. None of the distinctive Christian elements — atonement, Messianic identity, bodily resurrection into a transformed but continuous physical body — are present.
Attis of Phrygia, Adonis, Osiris, Tammuz
These are what scholars of comparative religion call the "dying-and-rising gods" theme — a category popularized by Sir James Frazer's The Golden Bough (1890). Jonathan Z. Smith, T. N. D. Mettinger, and the broader current of twentieth-century religious-studies scholarship have largely dismantled Frazer's category. What actually appears in the primary sources is vegetation deities whose "deaths" represent the seasonal cycle — dry summers, fertile springs — not personal, historical, bodily resurrection on a specific date under a named Roman governor. Attis is castrated and dies; his "resurrection" in some late versions is as a pine tree. Adonis is gored by a boar and descends to the underworld part of the year. Osiris is dismembered and becomes ruler of the underworld, not a king returned to earth.
These myths are annual nature rituals, not historical claims about a specific man. The gospel claim is altogether different — a specific Jewish rabbi, crucified under Pontius Pilate (a historically verifiable Roman prefect), buried in a specific tomb owned by a named man, raised bodily on the third day, witnessed by named eyewitnesses, in a city where his opponents could have produced the body.
The Jewish Factor
The single largest problem with the copycat theory is that the first Christians were Jews. First-century Jews were the most pagan-resistant people in the empire — they had died for centuries rather than bow to foreign gods. The idea that these same Jews suddenly adopted a pagan mystery-religion motif, transplanted it onto their own crucified Messiah, and convinced their most strictly monotheistic peers to accept this borrowing, is psychologically and sociologically implausible. The cultural soil was exactly wrong for the supposed borrowing.
December 25 — A Late Calendar Choice
The Gospels do not mention the date of Jesus' birth. The church did not celebrate Christmas on December 25 until the fourth century. The choice was made, most likely, because December 25 was the Roman festival of Sol Invictus (not actually the birth date of Mithras; that is a modern confusion) and Christians reappropriated the day as the birth of the true Light. The claim that "Christians stole Christmas from Mithras' birthday" is doubly wrong: Mithras had no documented birthday, and the adoption of December 25 as a commemoration was simply a missionary appropriation of a cultural calendar, not a theft of theological content.
What About the Resemblance?
Are there any resemblances between Christianity and pagan religions? Yes — but not the ones mythicists emphasize. C. S. Lewis, who spent his professional life in classical and medieval literature, observed that pagan myths about dying and rising saviors are good news bearing distant rumors of the real thing. Humanity has, since its earliest storytelling, reached for the idea that a god would become man and that his death could heal the world. The gospel is not a plagiarism of those myths. It is the historical reality they were reaching for. "The story of Christ is simply a true myth: a myth working on us in the same way as the others, but with this tremendous difference that it really happened." (Letter to Arthur Greeves, 1931.)
The theory of borrowing from pagan religions was given up by all serious scholars as early as the 1920s. It survives now only in popular literature, documentaries, and internet memes. — Summary of Ronald Nash, The Gospel and the Greeks
The "similarities" are almost all manufactured. The popular "chart" circulated online listing ten parallels for Horus, Mithras, Dionysus, and Jesus cannot be sourced to any primary ancient text. It appears to have been invented in the nineteenth century by Gerald Massey and embellished by Acharya S. (D.M. Murdock) in the twentieth. If you look up Massey's references in the Egyptian sources, they are not there.
Try the test yourself: take any alleged parallel — "born of a virgin," "twelve disciples," "crucified" — and look for it in the actual primary source. Tell me which Egyptian inscription, which Plutarch passage, which Mithraic cult inscription mentions it. The answer will almost always be that nobody ever could.
The Greek word mystērion appears twenty-seven times in Paul's letters. In every case its meaning is set not by Greek mystery religion but by Jewish apocalyptic literature — a mystērion is a formerly hidden divine purpose now revealed. Paul's usage maps to Daniel 2 (the interpretation of Nebuchadnezzar's dream as a "mystery" revealed to Daniel) and to the Qumran community's use of raz (the Aramaic parallel) for God's hidden plan now disclosed to his people. Paul is a Pharisee writing in biblical categories, not a mystagogue writing in mystery-cult categories.
The charge of syncretism collapses wherever the primary sources are consulted. Paul cites the Hebrew Scriptures on every page. His theological framework is Jewish to its marrow.