I wish to begin by saying that I am not making these posts to be "critical" in a negative way of TJS or its method, that is to be deconstructive, to nit-pick or to gripe. I am writing these posts to reassess the method, and to ask what the method actually can tell us, versus what it can't. And then I want to move forward with this thinking in a constructive manner. I do not know where the series will end up, since I am thinking aloud here. I don't have some grand solution in place already, but only wish to clear the decks and see what is left out there for The Jesus Project.
The dissimilarity principle (what I call the "apologetic principle") is about the strangest principle that could have been invented by scholars. Yet it has been the darling of most historical Jesus reconstructions. It works by trying to identify material that uniquely belongs to Jesus. The idea is that if a saying or action attributed to Jesus can be found in Jewish literature, then we must be skeptical about its attribution to Jesus. It could have been lifted by our gospel authors from the Jewish literature. Because of this uncertainty, the saying or action should be set aside. The same is true in the other direction. If a saying or action of Jesus is reflected in the literature of the early church, then we have to be less certain it originated with Jesus. So that material has to be set aside. It has been expressed this way by Norman Perrin: authenticity is most certain "if it can be shown to be dissimilar to characteristic emphases both of ancient Judaism and of the early Church" (p. 39, Rediscovering the Teaching of Jesus).
What is left? Well, it is considered the most likely authentically Jesus.
In evaluating this claim we first should recognize the irrational jump from "what is left" to authentically Jesus. There is nothing to suggest to us that the dissimilar leftovers came from Jesus himself rather than from an early charismatic preacher speaking in Jesus' name or an early Christian author inventing material along the way. Without some other evaluative steps, it is impossible to say who originated the leftovers. To say that they are even "more likely" Jesus than the material set aside is simply wrong.
Second we have created the most unlikely Jesus that we historically might conceive. He is a character completely out of whack from the rest of his first-century peers, from his culture, from his immediate past, and from his immediate future. This is why I call it the "apologetic principle" - because it allows us to create a Jesus who is not Jewish. He comes across as a person who, for instance, isn't kosher, who isn't concerned in fact about discussing or observing Torah at all. And he isn't early Christian - at least in the sense that the scholars have defined early Christians as millenarians. This is the way scholars get rid of the apocalyptic Jesus, and the embarrassment of a Jesus who might have been an end-of-the-world failed prophet. It was the early Christians who were the millenarians (not Jesus), so based on the dissimilarity principle, we can delete those sayings from Jesus' recordings that address an imminent coming of the end-of-the-world.
Because Jesus is left with no historical context or continuity, this means that we now have to invent for Jesus his own historical context, which we foist off as "Jewish" since we know that he was a Jew. Thus he is cast by the scholars as a Jewish Greek philosopher and beggar, even though we have no other known instances of Jews in Palestine acting as Greek philosophers and beggars wandering around the countryside teaching wise words and humorous stories as social critique to those who might listen.
What does the dissimilarity principle tells us? It might point out some of the variety of directions that the traditions of Jesus developed - that there was a need among the writers of the gospels to recall a Jesus who was not kosher, that there was a need among some early Christians to recall a Jesus who internalized the Kingdom. Whether these "dissimilar" ideas originated from Jesus himself or elsewhere would need to be subjected to more evaluation before any conclusion could be drawn. I have my suspicions about where and when these dissimilar ideas came into play, but that is for another time perhaps.
At any rate, it is not a principle that we would use to discover "authentic" historical information about any other figure in from the past, so why do we bother using it at all?