Why undesigned coincidences are not compelling to me

In #religion

An "undesigned coincidence" is used in an argument for the reliability of the Gospels, notable by Jonathan McLatchie, Tim McGrew and Lydia McGrew, and is defined as

When you have multiple (at least two) accounts that report an event where one account answers in passing a natural question raised incidentally by the other. Such features are evidence that a real event lies behind the reports found in the gospels — that is to say, the presence of an undesigned coincidence is more probable given the hypothesis of historicism than given the annulment of that hypothesis.

Here I am exploring an "undesigned coincidence" as described by Lydia McGrew:

About the grass being green mentioned in Mark at the time, and it's Passover time mentioned in John, and each of these is mentioned only in one Gospel. This fits together because the grass would be green around that time in Galilee. So an ur-source theory would be that there would be one source, not reality, that mentioned both that the grass was green and that it was Passover time. And that John just put down part of that and Mark just put down part of that, but it all came from this sort-of thing which was some version of the story that had both details in it. What Jonathan means about simplicity is basically what you've done is taken a hypothetical source and given it the properties of reality, and put it up there instead of reality and you have space between that and the alleged hypothetical source and reality where it could be false -- the source might or might not be telling the truth. Whereas if we just attribute these characteristics -- the grass and the time of year -- to reality it is simpler than attributing them to this lost documentary source. And then as he was also pointing out we have apparent discrepancies between the different accounts of the feeding of the 5000 which doesn't fit at all well with the idea of a lost source that by-jove looks like reality and people just took different parts of it.

Tracking this description a little bit more,

In Mark 6:30-43, we learn that the crowd sat down on “green” grass and in John, we learn there was “much grass.” In John 6:1-14, we learn the event took place when the Passover was at hand. The green grass corroborates the timing because the event likely took place during Israel’s rainy season, which runs from October through April. During the Passover in April, the grass would be abundant and green as it had been raining for months.

The argument seems to be that because Mark mentions green grass (which doesn't add to the plot of the story) and John mentions Passover and some grass, that the best explanation of this overlap is that the miraculous event of the feeding of the 5000 actually happened. Further that an "ur-source" which has both green grass and Passover is less likely, because we then have to posit the existence of a text or oral tradition that we don't have direct access to.

I am always supremely underwhelmed with these so-called coincidences, every time I've been presented with them -- they really do seem strained. For example, here are a few possibilities:

  1. Both the authors of Mark and John were there, noted the grass and Passover, and wrote their accounts from the shared experience (McGrew's theory)
  2. There was a text or oral story which mentions both the green grass and the Passover
  3. There was a story (oral or written) that just had Passover, and no grass, and through the process of oral tradition people added the grass (green or unstated) to make the story a bit more interesting. Note that this would be really easy, even if the event was an entire fiction, because those would know that Passover was typically green so adding that flourish would be natural. It's like adding snow to a Christmas story (in the US at least) even if the original story doesn't mention snow.
  4. There was a story where there was grass (no color given) and that it was Passover, and Mark adds the color as a literary flourish and doesn't mention the time because it was not important for that story
  5. There was a story about sitting on the green grass, and John (or his source) adds the particular festival for theological reasons, that Mark didn't seem to have.

The McGrews seem to think that the "ur-source" is positing a specific text that exists, rather than a process which produces texts. It is not the simplest idea to say that the events happened as stated, when we have other reasons to doubt them (e.g. miracles are unlikely) when we also have many known processes which could produce them, both with and without a separate text or oral tradition. I could probably envision several other possibilities for this "coincidence", but the point seems to be,

  1. We don't know the authors of any of the Gospels
  2. We don't know the details of the process by which they got their information
  3. We do know that several of them had copies of at least some of the direct texts, in addition to who-knows how many other sources
  4. We do know that there is strong indication that some of the Gospel writing was included for theological or literary reasons
  5. The actual posited coincidences are pretty weak.

This last point needs a bit of unpacking. The rainy season is stated to go from October through April, which is more than half the year. If you included a story that had green grass, you'd be correct about the "time of year" more than 50% of the time. John, in his story, doesn't seem to mention Passover directly. In John 2:13 he mentions "When it was almost time for the Jewish Passover" and then between that and the grass incident, we have phrases like (emphasis mine) John 3:22 "where he spent some time with them". Then John 5:1 "Some time later, Jesus went up to Jerusalem for one of the Jewish festivals." then John 6:1 we have "Some time after this," before the feeding. So, for the McGrews if the "undesigned coincidence" works in their favor, they can say there is an overlap. If it didn't, then it probably wouldn't be noticed. But even if noticed, it can be plausibly denied given the lack of specificity in the time on both sides of the story.

Someone who is convinced by these two passages as an "undesigned coincidence" I would be skeptical of many of their claims. I don't have time nor the expertise to go through each and every one of the so-called "coincidences", but they all strike me initially as being completely -- and trivially -- understood as being produced by a common process and are not strong evidence that the events actually happened.

A larger point also, is that even if there is agreement on the time of year, or even specifically a day of an event, that doesn't mean that the events actually occurred on that day -- it only implies that the story occurs on that day. It makes sense that Passover would appear importantly in many stories, both real and fictional, so "coincidences" which tie a story to that day do not say much about whether they are true or not.