I’m not sure whether this is a debate or a simple question. What is the currently accepted position of historians on the connection between Mithraism and Christianity? The two religions share a lot of similarities from what I’ve read: virgin birth, 25th December celebration, shepherds visiting, twelve followers etc (is this correct?).
However, how widespread was Mithraism? Is it conceivable (or likely) that Christianity borrowed beliefs from the followers of Mithras?
Have you been watching QI, by any chance?
No, but somebody on another forum that I visited has 
Both profess “Son-of-God-ism” and drew heavily on an already existing mystery-religion tradition. As annoying as The Golden Bough is, it documents a widespread “corn king” death-and-rebirth mythos.
It’s been hotly debated for centuries who borrowed what from whom. The Sol Invictus celebration, for example, predates both faiths as a minor Roman celebration, often associated with the Saturnalia (a bit more major a celebration), and Christianity, at least, targeted Dec. 25 for calendrical reasons that simply took advantage of the existing Roman feast. But much of the imagery associated with the Christian Atonement matches both elements of what accreted to Mithras piety and that pre-existent corn-king mystery religion tradition.
What is “QI”?
A program which has an appeal to SDMB types. Many clips on Youtube 
Note that Roman Mithraism (quite different from Eastern), came after Xtianity. It’s far more concievable that Mithraism borrowed from Xtianity. Roman Mithraism didn’t become popular until around AD200 or so.
The Feast of Sol Invictus was celebrated on the Solstice- that’s Dec 23rd, not 25th. Of course, calendars were a little screwy around that period. (That’s the whole point- the Sun is reborn, as it’s the Solstice). Saturnalia was celebrated Dec 17th through the 23rd. Big Holiday.
An early church theologian actually calculated Dec 25th as Jesus’s birthday. We now think he was likely wrong, but Dec 25th was one of a few calculated days that the early Church father had to pick from. Sure, it’s likely that that there being a number of rather big holidays around that time (Saturnalia, not Sol Invictus, see my point about Xtainity predating Roman Mithraism) was a consideration, but it wasn’t like “Hey, let’s just pick Dec 25th so we can compete with a Roman Pagan Holiday!”- as pretty well just about any day they picked would come within a few days of a Roman Pagan Holiday.
Don’t get me wrong. Xtianity certainly has borrowed symbology from other religions, and Mithraism could be one of them. But just as likely the other way around.
How is it annoying?
Do you have any cites for any of the the bolded bits? Many of these statements are directly opposite to information I have gleened from various scholorly sources.
Also, were you thinking of an earlier calendar when you said that Solstice was on the 23rd? The date on our calendar is either the 21st or the 22nd, this year it was the 22nd.
Under the Julian calendar, the equinoxes and solstices crept forward by about a day every 130 years. The Gregorian calendar stabilized them as they were at the time of the Council of Nicaea (A.D. 325), with the solstice around the 21st of December, allowing for variation due to time zones and our position in the 4-year and 400-year leap year cycles.
By a backward extrapolation, the solstice would have been around the 23rd or 24th at the birth of Christ. However, there is some controversy as to when leap years took place in the early days of the Julian calendar, and when certain months were lengthened, so one must not be too definitive as to the exact date of the solstice in any given year.
As Freddy sez,and I mentioned, The Solstice moves around, especially as the Calendar wasn’t stable then.
As to cite, here’s Wiki (highly debated)Mithraism - Wikipedia
Mithraism began to attract attention at Rome about the end of the first century AD. Statius mentions the typical Mithraic relief in his Thebaid (Book i. 719,720), around AD 80.
The earliest material evidence for the Roman worship of Mithras dates from that period, in a record of Roman soldiers who came from the military garrison at Carnuntum in the Roman province of Upper Pannonia (near the Danube River in modern Austria, near the Hungarian border). Other legionaries fought the Parthians and were involved in the suppression of the revolts in Jerusalem from 60 A.D. to about 70 A.D. When they returned home, they made Mithraic dedications, probably in the year 71 or 72.
By A. D. 200, Mithraism had spread widely through the army, and also among traders and slaves. During festivals all initiates were equals including slaves. The German frontiers have yielded most of the archaeological evidence of its prosperity: small cult objects connected with Mithras turn up in archaeological digs from Romania to Hadrian’s Wall…At Rome, the third century emperors encouraged Mithraism[4]. According to the 4th century Historia Augusta, Commodus participated in its mysteries: Sacra Mithriaca homicidio vero polluit, cum illic aliquid ad speciem timoris vel dici vel fingi soleat (“He desecrated the rites of Mithras with actual murder, although it was customary in them merely to say or pretend something that would produce an impression of terror”…Some would argue that because the Gospels are thought to have been mostly before 100 and that since very little is known of Roman Mithraism until after 100 that it is implausible to say that Christianity borrowed its doctrines from Mithraism; some have even suggested that Mithraism may have, in fact, borrowed elements from Christianity.[citation needed] But others suggest that it is more likely that similarities in practise go back to a common background in the Mediterranean world in the 1st century BC to 1st century AD. [6].
Originally, Cumont thought that Roman Mitraism came from the Persians. Now, this is doubted.
http://links.jstor.org/sici?sici=0075-4358(1998)88<115%3ATMOMAN>2.0.CO%3B2-7
“The Cumontian scenario would be hard to dispute, were the Mithraic
myths and rites demonstrably in place in Roman Mithraism at the time of
Tiridates’ visit. But they are not; there is in fact no evidence for them, or
indeed for any element of the Mysteries, prior to the 90’s, a generation
later…The stories from the 60’s postulated here for Mithraism were certainly told:
how else could they have survived in the sources? That they were current in
the Flavian age, when Mithraism, in my view, was founded, is for the most
part equally self-evident, although of course this or that detail might be an
embellishment of our immediate source.”
(The “Flavian Age” begins with Flavius Claudius Constantinus, known in English as Constantine II, (316 - 340) Roman Emperor (337 - 340).
To be honest, we don’t realy know. Theories and debates abound. Significant archaeological evidence isn’t found until around AD200. Mithraism was also a Mystery religion, and little written material remains.
The waters have been seriously muddled by some neo-pagans bringing back a modern form of Mithraisim, where they had to make up a lot from very little. As is common, they state these 90% made up items as 100% fact, including many of the “similarities” between Xtianity and Mitraism.
Rudyard Kipling thought that there was a strong connection, & wrote several works of historical fiction based on this assumption.
Proves nothing, but worth mentioning.
I shall correct you before Mr. Fry does ! It’s programme not program.