The great and intimidating thing about writing a book on theory and method (although I loathe that term) in HJ studies is that you regularly gain new insight into those matters oneself. Then one wonders how one ever did the work of HJ studies before that insight.
I have in the past used the terms "coherent" and "intelligible" as more or less synonymous. About ten minutes ago I realized that there is a conceptual benefit in differentiating between coherency as the condition in which a historical hypothesis is internally consistent with itself and intelligibility as the condition in which a historical hypothesis renders an account in which human agents operate in an intelligible fashion. Let me expound.
Efforts at harmonization are very frequently coherent. If I take the two canonical accounts of Judas Iscariot's death I can create a quite coherent narrative. Matthew tells me that he hung himself. Luke tells me that he fell headlong and burst open. It is quite coherent to say that Judas hung himself and then his body fell headlong and burst open. Is it intelligible, however? Whilst I could imagine Matthew leaving out the part about what happened to Judas' body post-mortem it seems a major lacuna on Luke's part to leave out the matter where Judas committed suicide. It seems to me that a more intelligible account would suggest that there was in early Christianity some diversity of opinions regarding Judas's death.
Or take the cleansings of the temple. It is altogether possible that Jesus cleansed the temple twice, once at the beginning of his ministry (as per John) and once at the end (as per the Synoptics). Yet this would mean that each Evangelist fails to mention that this event happened at least twice. It is coherent, sure, but perhaps at the expense of rendering the Evangelists' operations less than intelligible. Perhaps more intelligible, and no less coherent, would be to argue that either the Synoptic tradition or the Johannine, or both, has for literary or theological purposes placed the cleansing in a location other than where it occurred in Jesus's ministry.
Anyways, just really thinking through this insight about coherence versus intelligibility. I'll see where it takes my thinking in the future.