Apologists have always argued that the canonical gospels were written soon enough after Jesus' life that they can be considered historical rather than mythological or legendary. Recently, I have been running across more bloggers asserting that it took two or more generations in the ancient world for historical facts to be replaced by legend. Moreover, they seem to believe that this principle is widely accepted among historians with one going so far as to suggest that is "unassailable." Although I know this argument has been around for awhile, I have to suspect that guys like Strobel have been hammering it in their sermons with increased vigor lately.
My initial reaction to the argument was to wonder how someone could ever come up with such a principle in the first place. I would think you would have to have some sort of model of how a legend develops. In order to build such a model, you would need some very detailed information about how specific legends had developed in the ancient world under various circumstances. I think you would also need to have a lot of information about any particular story that you wanted to test for conformity to the principle.
It did not take much googling to find that the source of this principle is a book titled Roman Law and Roman Society in the New Testament by an Oxford scholar named A.N. Sherwin-White. However, I did not find anything that gave me much clue to how he derived this principle. I found some references to a study of the works of Herodotus but no details of what the study involved. Most apologists simply made an argument from authority.
I was also intrigued by the fact that I did not run across any skeptics who provided much detail about Sherwin-White's work. If there was some flaw in his methodology, I would have expected to come across some atheist who took delight in slicing and dicing his conclusions. On the other hand, if his study was really persuasive, I would have expected the apologists to go into a lot more detail about his findings. I am quite perplexed.
So I guess I am going to have to read Sherwin-White's book myself. I put in a request through inter-library loan so hopefully my local library will be able to get it for me from one of the local colleges that have it in their catalog. I will try to keep my biases in check while I read it.