Everett's Many Worlds model is, in its own way, a form of radical constructivism. It implies that each individual has a timeline, and every timeline determines an entire universe, in which decisions about indeterminate events is resolved only for those moving along that timeline.
So not only does my entire reality depend upon how I make sense of it, but hordes of different versions of me create whole dimensions of alternative ways of making sense of it. In a more classical framing, all of those worlds are not duplicates of each other with minor variations, but exist as matrices of details that are only partially determined until they meet an observer.
Given that notion of a coherent observer collapsing undecided past events, a la Schrodinger's cat, who is to say that any of those decisions are made on their own before I personally do something that requires them to be decided? Basically, we can presume that no past event affecting me is truly determined before I understand it.
Then not only are understanding and acting intertwined, but actual history is undecided until action meets understanding.
This becomes bizarrely solipsistic unless one also accepts some notion of intersubjectity, where my understanding of your existence, and your understanding of the past then presses me to share a partial understanding of the past, so that we agree on the vast majority of these past events.
That is best captured, in my opinion, in something like Leibniz notion of monads. Shared reality consists of feedback loops between your subjective realities and mine. Each of our subjective realities is projected onto each other's and we accept partial versions of each of our associates' subjective worlds and mediate a position of our own.
Whitehead's systematization in "Science and the Modern World" is largely a resurrection of Leibniz in reaction to the theories of relativity and quantum mechanics and the feelings of relativism in a matrix of overwhelming interdependence that dominate modern life. One way of reading this kind of thing is as a pure idealism, but an alternative is as radical constructivism with a strong form of intersubjectivity.
