Matthew 22 and Mark 12--Same story as Luke 10?

Had a good follow up question to my post yesterday in relation to the Parable of the Good Samaritan in Luke 10:

I have a question about the Matt 22 and Mark 12 stories. The Matthew and Mark versions seem obviously parallel in my opinion, but the Luke version is different enough from both (who answers the question first, adding the Samaritan parable, and the ending of the Mark story is unique). I realize that the writers may have framed the story to fit their gospel, but are these versions different enough to no longer call them parallel? ... I am just asking first, what is the standard for calling passages parallel? Second, what kind of hermeneutic is there for these parallel passages in the gospels or in Samuel/Kings/Chronicles?

My response:
Great question!

From the standpoint of interpreting Luke (or Mark or Matthew) you will want to let each gospel have its full rein. This means to think of Matthew, Mark, or Luke at these points as a self-contained, literary text. If you think first of Matthew, Mark, and Luke as giving videos of the events, that is, as transcripts of exactly what happened, then you will get off into harmonizing them and will miss the unique points that gospel is making. It's like what we tend to do with Christmas plays or Passion plays. Each gospel has a unique message in relation to these parts of Jesus' life and we miss them if we do not read each independently of each other first.

I'm sure you know that most think Luke and Matthew used Mark as a major source behind their gospels. That presents us with a question when it comes to incidences like this one. We have two basic choices:

1) we consider this unique Luke material that he got from some other source--and certainly this is the way most scholars, even very skeptical ones like John Dominic Crossan, view the Parable of the Good Samaritan. Tom Wright might say that Jesus probably taught similar things in different contexts in slightly different ways, so who is to say that this isn't simply a similar situation passed on independently.

2) The other option--and one made more likely by the fact that Matthew and Luke seem to use up almost all of Mark (only 31 verses of Mark aren't found in them somewhere) is that this is Luke's creative re-presentation of the same story in order to present the Parable of the Good Samaritan, which he knew from some other source.

You will have to choose which scenario you think is more likely. The truth of Luke 10 remains either way.