Context : CriticalRationalism
So here's my interpretation of "World 3" which is obviously related to my interpretation of Popper's CriticalRationalism etc.
So ... Popper takes the problem of justification (RejectingJustification) and turns it backwards. Rationality is not defined by an infinite regression of justifications back into the past, but instead is defined by a propensity or CounterFactual properties of the agent. The critically rational agent is just the sort of thing such that if new evidence comes in, it will change its opinions.
But ... much contemporary philosophy focuses on trying to identify the limits of this capacity to learn from new evidence and improve knowledge. The project is an analysis of HumanNature or "language" / language game or culture or social group (or even when infected by IdentityPolitics things like "race" or "gender" etc) implicitly charting and deducing the limits that these place on the capacity to react to experience. OptimisticAndPessimisticEpistemology
Now Popper, I am sure, is not unaware that we do have physical limits on our capacity to perceive and receive counter-evidence. And he briefly gives a counter-argument at one point that we can build new instruments to measure things we can't perceive with our human senses. (And of course, we can now imagine MachineLearning systems and ArtificialIntelligences able manipulate data and conceptualize ideas beyond the capacity of our puny brains.)
The pessimists can obviously easily turn around and say "sure, humans can augment our capacities with our computers, but the total system of human + computers still has a limit"
And this is where the cleverness of Popper's "three world's model" kicks in.
Because most people think of this as an either / or thing. Either the "pessimists" are right. And knowledge is limited by our physical constraints. Or the optimists are right and we can keep augmenting ourselves.
But Popper chooses a both / and solution to this "problem". He declares that there is both a realm of knowledge that is defined by the constraints of our physicality or facticity etc. AND there is a realm of knowledge that is defined by an in principle limitless / infinitely extensible epistemic subject and the propensities it has to revise its beliefs when confronted with new information.
These realms are World 2 and World 3 respectively.
And the really interesting thing is that they ARE "worlds". And that the gap between them is of the same metaphysical or conceptual order of magnitude as the gap between World 1, the realm of law and physical states, and World 2, a realm of mental states or space of reasons.
What is the relationship between World 2 and World 3? Well, just as World 1 objects or physical states can be thought of as "vehicles" for World 2 objects or mental states, so World 2 objects (beliefs) can be thought of as "vehicles" for World 3 objects (the entities of objective knowledge)
We as limited physical things, individuals or even collectives of us, augmented with our machines, can never have "objective knowledge" as such. We can only have subjective knowledge in our World 2s. But these World 2 objects are themselves vehicles for World 3 objective knowledge which are the beliefs of the infinitely extensible, open-ended critically rational epistemic subject. Which grows through the interactions of all possible limited physical things.
Of course, such World 3 objects require that they can be "externalized" from the limited particular system that holds them. Whether they escape individual humans through speech and writing. Or whole cultures through being encoded in whatever Rosetta Stones that are needed to translate and join them to the "outside" beyond our current limits.
See also :