Question: I read that centuries before Jesus' birth, Mithras was born of a virgin, in a grotto or manger, and was attended by shepherds. Did the Christians steal their ideas from the ancient Mithras religion?
Response: There are many claims like this - that Christianity supposedly stole beliefs and practices from various pagan religions. This is my advice for evaluating claims like these:
1. Find out if the alleged similarities are genuinely similar.
For example, let's consider the claim that Mithras was born of a virgin, like Jesus. The story of Mithras is that he was birthed from a rock, under a tree, by a stream, as a full-grown adult, wearing a hat, and holding a knife, before time itself began. Obviously, the story of Mithras' birth is very different from Christianity.
2. Find out of the alleged similarity is even true.
For example, let's consider the claim that the birth of Mithras took place in a grotto or manger and was witnessed by shepherds. The legend of Mithras is that he was born out of a rock before time began. Shepherds would not have existed yet. And there would have been no need for grottos or mangers.
3. Find out the earliest evidence for the alleged similarity.
Regardless of whatever claims are being made about Mithraism, the fact is it would be extremely difficult to prove that any of them actually predate Christianity.
There are mentions of a pagan god named Mithras that are older than Christianity. But, most of what we know of Mithras comes from evidence that is younger than Christianity.
The ancient followers of Mithras left behind no religious texts. So, we have to speculate on their beliefs. And scholars do this by studying hand-made images found within ancient Mithraic places of worship. These scholars generally conclude that few if any of these places of worship were built earlier than the middle of the Second Century A.D.
At that point in time, the books of New Testament were already in wide circulation. And, early church leaders had long since been circulating letters amongst themselves, citing passages from these books to help explain aspects of Christianity.
Christian writings that explained Christianity and its beliefs, in detail, were already widespread by the middle of the Second Century.
So, even if there were any actual, meaningful, similarities between the beliefs of Mithraism and Christianity, the evidence would indicate that Mithraism borrowed from Christianity, not the other around.
See related articles at About-Jesus.org:
• The Da Vinci Code - the book, the movie, the deception
• Was Christianity influenced by paganism? - an article on About-Jesus.org