AP: Well, this is a very difficult question to answer because there are so many parables and there are so many types of parables. Scholars often argue that the parables can be attributed to the historical Jesus, while allegories are a creation of the early church. The early church usually tried to allegorize the parables so that, by not viewing them solely as comparisons and seeing in them referents that were symbolic and stood for something else, they could milk more out of them than was actually there.
Since spread the Gospel of Mark, which explains allegorically the parable of the sower (Mark 4:13-20: such clarifications are probably not the actual words of the historical Jesus, but explanations provided by Mark) it became commonplace in the Great Church to interpret the parables not as comparisons, but as allegories.
In general, it can be said that almost all the parables, at their core, come from the historical Jesus. But what Jesus actually said is not always as they appear in the Gospels. One thing is what Jesus actually said in his parables, and the other one represents how, based on the oral tradition that came later, the parables were slightly and sometimes significantly modified by the church. Sometimes, for example, they turned them into allegories and, in doing so, significantly changed the primary context in which they were spoken.
Some examples of this possibly include the primitive comparisons of Jesus, which are now lost, and those in the Fourth Gospel, such as the "Good Shepherd" (John 10:1) and "Jesus like a vine, and the disciples like the branches" (John 15:1),which contain secondary allegorical elements. The attentive reader will notice that John is mixing his ideas with a possible parable of Jesus.
The converse is also true. A parable could be a completely invented story. For example, a lost parable about a bad tree that finally rots away could have led to the story of Jesus cursing the fig tree because it had not produced fruit figs (when it wasn’t the season for it to bear fruit) (Mark 11:13). Consider another example. The extremely poor woman who gave alms in the temple; she gave everything she had to live on (Mark 12:44). That this is an invented story is clear because, as we know, nobody was sitting in the temple. Sitting in the temple was disrespectful to God!); alms were apparently placed in a different way in the temple; moreover, Jesus was far away! How would he have been able to see that she gave exactly this amount and how would he have known that was all the money that she had?
TWH: The Gospels are inspired by God. A real dividing line exists here between myself and Antonio. Each of us views the New Testament in a different light. While Antonio believes that the canonical Gospels are wholly human in origin, I believe that they have a divine origin and a human medium, the nature of which allowed the human channel to bear his own style and characteristics without in any way, shape, or form hindering or nullifying the veracity of what God wanted to communicate and did communicate in them.
Robert H. Stein has a section dealing with the authenticity of the parables in his book An Introduction to the Parables of Jesus (Philadelphia: The Westminster Press, 1981 [see pp. 38ff.]). He reasons that the parables are authentic because they "meet the 'criterion of dissimilarity' or 'distinctiveness'" (38). He continues, "This tool, used widely in recent life and teachings of Jesus research, has certain weaknesses, but it is nevertheless helpful in establishing a minimum of authentic material that scholars are willing to accept as authentic" (38). I mention that book because the author taught for many years at a seminary connected to the one where I studied–one that affirms the inspiration and inerrancy of the Bible. When it comes to the authenticity of Jesus' parables and sayings, I don't go the route of Stein. As for me, I start with biblical inspiration. Is the Bible–and specifically the New Testament, and, even more specifically, the Gospels–inspired by God? Does "everything that is written down" (πᾶσα γραφή) ultimately have its origin in God (θεόπνευστος)? Do we have the record that Matthew, Luke, Mark, and John wanted to give us, or was God involved in the process of revealing to us through these men what he wanted us to know about the life and ministry of Jesus? Indeed, the Bible is inspired. From there, I know that the Scriptures must bear the very character of God in what they reveal. It is impossible for God to lie. Building on that, the Gospels do not present events as historical that did not occur. (Of course, I'm not talking about issues of textual criticism). No such events are presented.
So, our starting points are totally different. One starts from the position of a skeptic, one from the position of biblical inspiration. I do not utilize the pieces of historical Jesus litmus paper to measure dissimilarity or distinctiveness. I don't approach God's Word that way. I don't stand over it and subject it to the norms of today's human wisdom. Which of Jesus' parables and sayings are original? –Those presented in the Gospels of Matthew, Luke, Mark, and John.
My own book that deals with one of Jesus' sayings (Luke 6:40 and the Theme of Likeness Education in the New Testament [Eugene, OR: Wipf and Stock, 2014] starts off this way:
"Studies concerning the Sermon on the Plain (SOP), Luke’s complement to Matthew's Sermon on the Mount (SOM), are primarily entangled in source-critical discussions (i.e., which author used which source and for what reason). Because of the amount of attention given to this interpretive method, less attention has been given to other aspects of biblical interpretation in studies dealing with the SOP, such as lexical, syntactical, structural, and rhetorical analyses. One victim of exegetical neglect is Jesus's 'proverbial maxim' concerning the teacher-student relationship (Luke 6:40). It is one of the most important New Testament (NT) texts dealing with Christian education, second only to the Great Commission (Matt 28:19–20).
'An apprentice is not above his or her teacher; but each one, after having been fully trained, will be like his or her teacher' (Luke 6:40). This verse has been quoted, cited, and referenced in vast amounts of Christian education and discipleship literature. Nevertheless, the verse is nearly untouched in exegetical discussions with the exception of source-critical analyses. These discussions are primarily concerned with (1) where the saying originated, (2) whether Luke's or Matthew's form of the saying is original, and (3) how different forms of the saying (see Matt 10:24–25; John 13:16; 15:20) are used in their respective texts. Some have even suggested that this verse lacks cohesion with its context, leaving interpreters dumbfounded as to how it functions in the paragraph- and section-levels of the discourse." (1-2)I argue that the saying found in Luke 6:40 is an authentic saying of Jesus and is historical to the Sermon on the Plain/Mount, exactly where Luke places it. It was not picked up by Luke (e.g., from Matthew) and simply dropped into the narrative because Luke felt so inclined to do so as an author and a historian, as some have supposed. And it was not invented by Luke or the early church. Jesus actually said it.