A-Priori... a lovely place to visit but you wouldn't want to live there
Imagine a physical world filled with creatures, places and things, where time, for the most part, moves forwards. Now in addition to this physical world, add the capacity for a world of behaviours. These behaviours do not exist in the physical world, as the physical world is made of physical stuff. These behaviours affect the physical world, however, in a myriad of interconnected and complex ways.
Creatures, of course, both are made of physical stuff and have behaviours, and the physical stuff which makes these creatures up all have behaviours, and so on ad infinitum, so ultimately it makes no sense to separate the physical side of a creature from the behavioural side. So, let us assume that there exists some mapping from the behavioural world onto the physical. Let us assume for all creatures that they were created out of previous interactions of behaviours between a theoretical, Occamesque atomic physical unit. The same goes for places, which can be regarded as creatures of a different nature, as with things. Let us seed this world with all manner of stuff, and endow that stuff with behaviour. Let us call the combination of stuff and behaviour a 'creature'.
Time, paradoxically, exists almost purely as behaviour, albeit quite complex. Let us consider time not as a dimension of physical space, but as a soup within which we all swim. By 'we all', I mean you, me, and the behaviours and physical stuff. Time is the mapping not only between our world of stuff and behaviours, but also of us, the interactors with this world.
It is, of course, inefficient to record the previous states of all instances of all creatures, as some creatures' states are largely irrelevant. It is important for many of the creatures to have histories, but there would be so many of them that would have much in common that is more efficient to create shared histories. It would also be efficient if the world had a set of behaviours for amalgamating further histories on its own.
To simplify the following, I shall refer to this new world of both things and behaviours as A-Priori. I shall of course refer to A-Priori's physical component as A-Priori.P and its behavioural component as A-Priori.B.
It is important to recognise that although we exist in 'the real world' (TRW) we can create or influence behaviours with behaviours of our own (be that by writing new code, deleting old code, or by some other means); thus we exist in both TRW and A-Priori.
As interactors with A-Priori we will be able to do the following.
We start by seeding a world with initially a geography and associated behaviours (including weather). Then we provide a theme (i.e., collection of common narratives, behaviours (such as gravity, magnetism, magic, mutation rates)), and then characters with specific histories and behavioural patterns, and swarms of generic characters with generic histories and generic behaviours.
Examples of behaviours which characters may possess include flocking (a desire to be near your mates without crashing into them, tempered by a desire to keep moving), breeding, grouping (similar to flocking but less motivated by movement), movement, aging, the ability to experience surroundings, etc.
Obviously many simple creatures will have to be created and generified, forming larger, more complex creatures. For example, the ability to perceive the world around you could rest with your eyes, and thus by adding (instantiating) different types of eyes to a creature, you give that creature an ability to see the world. Different eyes would lead to different views of life. A camera becomes a type of eye which consumes film and produces photos. There could be some sort of magic involved; in fact there should be. Further detail can be added at will.
Behaviours such as mimicry tempered with the evolutionary mechanisms of mutation, innovation and auto generification of behaviours and their histories will give rise to a myriad of glorious new behaviours, which can be 'bred up' to suit.
Behaviours such as communication, while more complex, can be seeded initially then allowed to evolve in new and interesting ways by further human intervention and by seeding the system with further narratives and examples for evolution to feed upon.
Narratives must be expressed in languages comprehensible to the creaturesto whom they are relevant; this would start simply and grow complex quite quickly as the system is seeded and trained.
This framework would give us the building blocks for exploration of all sorts of philosophy, speculation and experimentation, as well as allow flexibility for worlds and characters with multiple themes, genres and worlds within worlds.