Taking about Kegan's stages isn't easy. Using the stages means judging other people and people don't like to be judged. They especially don't like to be judged as not yet being on stage X. That said I will speak anyway, if you don't like what I'm saying and find it judgmental feel free to just ignore it.

On of the predictions of Kagan's model is that when I'm faced with a person who believes in one model to explain everything, I'm unlikely to be able to move them via rational argument in a single interaction towards not being attached to a single model.

David Chapman wrote good articles debunking Bayesianism as not being able to explain everything but a stage 4 person who reads them usually can't simply accept them because moving to stage 5 involves a lot more than just exchanging one belief.

Kegan's model also suggests that it's pointless to have that debate about people who are at the stage 3 to stage 4 transition and for whom a framework like Bayesianism can be very valuable because it gives them a structure to think about the world.

On my local LW dojo I think most participant are capable of stage 5 thinking and plenty of people on this website are also capable to have a debate on that stage and can think in those abstractions. Some people however aren't. At the facebook group the amount of people who aren't is even higher.

That put my sometimes into the role of advocating Bayesianism at one discussion because I was dealing with someone for whom it's an improvement and a step in the right direction and the next day speaking about the flaws of Bayesianism and taking it as a system to explain everything.

Someone between stages 3 and stage 4 will hear when I speak about the flaws of Bayesianism that I want to say that it's a flawed system and there's a better system. But that's not what I'm advocating in those circumstances when I want to make the general point of not attaching oneself to one system as happens in Kegan's stage 4 but being between systems.

In the spirit of what Saul A. Kripke writes in Naming and Necessity: It really is a nice theory. The only defect I think it has is probably common to all philosophical theories. It's wrong. You may suspect me of proposing another theory in its place; but I hope not, because I'm sure it's wrong too if it is a theory. And that doesn't mean stage 3 relativism.