Doctrine is spelled "doctrine", not "doctorine". There is no Roman Catholic doctrine that teaches of the "Virgin Mary having deity".

@joehinkle11 when you say early Christians, do you mean the first 1500 years? Or simply what was the cause of this doctrine that lasted 1500 years. I also think you would be hard pressed to find arguments to your points in early Christian writings because, well, quite simply there was no arguments. The sacrifice of the Mass is propitiatory in the manor that the sacrifice at Calvary is propitiatory, the reason being is that it is that one and same sacrifice. This is a nice change in perspective from , Why did later Christians deny the real presence, I actually love this question.

@Marc I mean pre-Nicene Christians. And since there were no arguments recorded, I'm looking for any sort of theory about why they believed in the Real Presence. One theory would be Jesus directly taught the doctrine, but this is unlikely to me. So I'm curious if there are any other theories of where they got this idea.

You have provided no evidence that the early Christians believed in the Real Presence. I believe this question is based on a false premise.

I'm voting to close this question as off-topic because it assumes something that it doesn't demonstrate, and that is probably false: that the early Christians believed in the Real Presence doctrine. In other words, it is a question likely based on a false premise. If it asked why certain Christians believe the early Christians believed in the Real Presence, then it would be on-topic.

@Lee you shouldn’t vote this as off topic just because I assumed the historical fact that Christians from the 2nd century onwards believed in the real presence.

Re: Update 2: Just because major Christian denominations believe and assert that the early Christians believed in the Real Presence, that doesn't make it a fact of history. Denominations have strong motivation to interpret history according to their own doctrines. Protestants argue that the early Christians believed in justification by faith alone, even though we know that their doctrine historically originated with Luther. Catholics, similarly, have a strong incentive to read early church fathers as supporting their doctrines.

I used the word "assume" because that's the word you first chose. There are many Christians from the 2nd century onward who speak about Christ truly being present--whatever that means or entails. There are no Christians arguing against that view. From a historical point of view, it is historically factual that this was the general belief of Christians which clearly develops at least from the 2nd century onward. If you are personally disturbed by this fact, you shouldn't be answering questions related to it.

I would advise that if you accuse me of "assuming" bad history as you are that you back up your claims.

From Wikipedia: "Eucharistic theology as a branch of Christian theology developed during the medieval period; before that, during the early medieval period theological disputes had focussed mostly on questions of Christology." I.e., the doctrine of the Real Presence wasn't formulated until medieval times at the earliest. Back-dating it to the early church fathers because they said some things that sound sort of like it is bad history and bad doctrine.

Is the OP assuming that "Real Presence" is the same thing as the "Catholic Mass" (aka Transubstantiation) or as two completely separate ideas (which is what they are)?

Once again, Catholics and others who today hold to some variation of the doctrine of Real Presence may believe that some or all of the early church fathers believed in it. Others (such as yours truly) dispute them on this, just as Catholics and Orthodox dispute Protestants' reading of penal substitution and justification by faith alone into the early church fathers' writings. So once again, for the question to be on topic, it needs to be scoped to Christians (or Catholics specifically) who believe that the early Christians believed in the Real Presence.

I'm using the term "Real Presence" in the sense that Christ is not merely symbolically or metaphorically present, but really present. So no, I do not mean "Real Presence" in the sense of it being the Catholic Mass or Transubstantiation. For example, a Lutheran believes in the "Real Presence" while denying both those Catholic doctrines.

@Lee I would appreciate it if you looked at this historically and not theologically. I'm not asking theological questions here. I'm asking historical ones. There are not "Catholics" or "Protestants" in the 2nd century.

Then it becomes so vague as not to have much meaning. "Real Presence" is a specific doctrine, or set of doctrines, developed at a specific time in Christian history. Either you're asking about that doctrine or you're not. And if you're not, you shouldn't use the term "Real Presence." I would venture to say that nearly every Christian denomination believes that Christ is really present when they take the eucharist. But "Real Presence" is about the elements of the Eucharist actually being Christ's body and blood in some way.

@Lee You quoted a Wikipedia article which mentions that a branch of Christian theology dedicated to the Real Presence developed in the early medieval period as some sort of proof that the Real Presence wasn't believed by Christians prior. I hope you see that a branch dedicated to studying the Real Presence isn't the same as the existence of the belief in the Real Presence.

Please avoid personal attacks here. If the doctrine of the Real Presence wasn't developed until medieval times, it is anachronistic to say that the early Christians believed in it. What you're basically asserting is that the doctrine of the Real Presence was developed before that time. If so, then the Wikipedia article is wrong, and should be corrected. But I don't think it's wrong. I think that present-day Christian denominations and their apologists are back-reading a doctrine into times that it didn't exist.

Once again, you can ask for evidence that this belief existed in the early church, and you can ask why those who believe it existed in the early church think it did. But when history says that the doctrine of the Real Presence was developed many centuries later, you can't simply assume that it existed earlier, and ask a question based on that assumption, because many Christians disagree with that assumption, and such questions invite answers that argue that the premise is wrong.

@Lee Many historians believe that early Christians believed in a primitive understanding of the Trinity--especially ideas stemming from the Gospel of John. It would not be anachronistic for me to ask a question about the early Christian understanding of the Trinity.

@Lee this is not a forum for us to debate history. Most historians already agree with my view that early Christians from the 2nd century onward believe in the Real Presence--whatever that exactly means or entails. Please do not use this venue as a place to debate history.

"Most historians" does not make something a fact. The very word "most" admits that there are historians that disagree. And by the same token, there are groups of Christians who disagree. Assuming that those Christians are wrong is both contrary to the general policies of this site and, once again, an open invitation for answers that argue against your premise.

Bottom line: Your question as currently written is off-topic here because it assumes as fact things that not all Christian denominations agree with. (Specifically, not all Christian denominations believe that the early Christians believed in the Real Presence of Christ in the Eucharist.) I've explained to you how you can make your question on-topic. That's all I can do.

I am making no claims in my question as to whether or not the doctrine of the Real Presence is true or false. I merely ask what caused men like Ignatius and Justin Martyr to make statements which strongly suggest that they believed in the "Real Presence." I make no judgement as to the exact meaning of these men's statements and no judgement as to whether or not they were correct in their beliefs. My question was only historical and theoretical.

@Lee I am making no claim about theology so there is no possible way that I could be in conflict with even the fringest of Christian beliefs. Just because some Christian doesn't like history or what Justin Martyr said doesn't mean my question should be labeled "off-topic".

I don't think this question is likely to be closed as off-topic, but @LeeWoofenden is certainly entitled to his well-reasoned opinions. The hardest part about it is going to be the lack of concrete evidence.

As a Catholic, I believe that almost all my Traditions were handed on bottom-up, not top-down and therefore unlikely to be necessarily found written down.

The Real Presence of Christ in the Blessed Sacrament had to have been one of those things. We explain it to our kids the same way, "here's where the Priest turns the Bread into Jesus Body". I can't imagine any other way to pass on that sort of teaching.