Advantages of having an explicit theory of change:
Makes it easier to sync up about direction/priorities/reasons for doing things
Makes it easier for people to engage critically, or otherwise to notice mistakes and course-correct
Disadvantages of having an explicit theory of change:
Easy to have the case where your best expression of something is dumber than your real internal sense of it
In this case it may be preferable to be guided by the internal sense rather than the explicit version
(this is at least some distant relative of Goodhart’s law)
To the extent that you’re going to be guided by your internal sense rather than an explicit version, sharing something as an explicit theory of change can be misleading
In general I think it’s good to encourage lots of explicit discussion about theories of change
Ideally without committing to reaching an “answer”, but having that as a goal may be helpful for prompting the discussion
I think that I find the disadvantages quite emotionally resonant, which may pull me to err too far in the direction of not being explicit. I have appreciated some cases where people have pushed me towards “let’s have a discussion where we’re pretty explicit about best guesses”.
Here’s a quote from a comment Owen Cotton-Barratt’s made elsewhere (focusing on explicit theories of change in general, rather than specifically ToC diagrams):