Being able to distinguish between biographical facts about Jesus’ life and the theological and literary elements of the Gospels can, to a certain degree, allow an element of autonomy in each distinct area of inquiry. A person interested in the historical facts does not necessarily have to worry about conflicts with her own faith’s theological doctrines. A person interested in theology does not need to be threatened by historical challenges to their interpretations. Without these dangers it seems like some mutual enrichment is possible. The opposite would seem to be the case; if the two methods of inquiry are autonomous than how can they be mutually supporting. However, my argument is that they don’t need to see each other as a threat and can therefore move forward using what the other provides. So a historian can make judgments about the sorts of things Jesus may have said to His followers and the way His movement worked in relation to other movements with awareness of what theological beliefs exist about these things. And the person interested in theology can understand the full meaning of the themes of the Gospels in relation to the historical conditions which brought them about.
The reference to Psalms 110:1 which is used to explain David’s relation to the Messiah in Mk 12:35-37 seems to be a clear instance of using existing Scripture to explain Jesus’ role. This is an interesting case because Jesus is literally in the Temple area quoting Scripture. At first glance this makes it seem like Mark is not making this reference himself but is just quoting Jesus. In order to know how much literary freedom Mark is taking here it would be useful to know if Jesus’ earliest disciples already called Him the Messiah without controversy among themselves (because this would hint to whether Jesus spoke extensively to the issue of being the Messiah – Mark seems to indicate He kept it hidden at other times) and perhaps some knowledge of whether Jesus was educated enough to have Scripture memorized like that. This is just one example of how knowing some historical facts can give us the tools to know the extent to which something is interpretation or is very exactly based on Jesus’ literal actions or statements.