The hinge is agency
The hopeful end touches the darkest one.
At +3, the best future looks less like a hero story and more like agriculture or industrialization: a disruptive, civilization-organizing shift measured not in protagonists but in statistics. More people living longer, beyond subsistence, with room for creativity and progress. It is the movie nobody makes, because diffuse progress has no third act.
Uplift and subjugation can produce the same outcomes. The difference is whether people still get to decide.
±4, where the circle closes: a benevolent superintelligence that decides for us. In Colossus and Minority Report the handover is voluntary; subjugation arrives without a war. Banks’ Culture is the kind reading of the same position. −3 is the scenario the researchers fear; ±4 may be what happens if things go exactly the way they want.