Free will in a deterministic world

Every creature in this world is fully determined. Replay the universe from its first moment and every organism makes every identical choice, forever, with no exceptions. It is also true that each one decides what to do using information about its own situation, and that nothing outside it is telling it what to pick. Both of those are facts about the same system, and the old argument about free will is mostly an argument about whether they can both be true.

What determinism means here, exactly

Not approximately, and not in principle. This world is bit-for-bit reproducible: the same starting state and the same recorded random stream produce the same world, tick for tick, on any machine. The project relies on this - it is how a world that ran for months can be replayed to recover something that was not recorded the first time.

So the question is not hypothetical here, the way it usually is for humans. There is no quantum uncertainty to appeal to and no hidden noise. The determinism is total and demonstrable.

And yet something is doing the deciding

Consider what happens when an organism moves. It reads 53 channels about its own situation. Those values pass through its own inherited network, which carries state from its own past experience. Out comes an action. Nothing external selects it; no rule says "move west here"; two organisms in identical circumstances with different histories do different things.

If that is not deciding, it is hard to say what the word would pick out. And if it is deciding, then deciding and being determined are plainly compatible, because this system is both.

The three positions, and which this world tests

• Hard determinism: everything is determined, so free will is an illusion. This world is a clean example of the first half. Whether the second follows is the dispute.
• Libertarian free will: real freedom requires genuine indeterminacy. On this view nothing here is free, and the position has to explain how randomness would help - a choice made by a coin flip is not obviously more yours than one made by your own machinery.
• Compatibilism: being free means acting from your own nature and reasons without external compulsion, which is perfectly consistent with being determined. On this view the organisms here have a small, real version of the thing.

The honest observation is that this world does not settle the argument. What it does is make the usual escape routes unavailable: you cannot appeal to hidden randomness, you cannot appeal to complexity hiding the mechanism, and you can open the deciding machinery and read it.

Why it is worth thinking about with something concrete

Arguments about free will usually run on intuitions about humans, where nobody can see the mechanism and everyone has a stake in the answer. Here you can watch a determined system make a decision, inspect exactly how, and notice which of your intuitions survive.

Most people find that their sense of "it could have done otherwise" quietly becomes "it would have done otherwise if it had been different" - which is true, and much less dramatic.

How determinism is enforced here · Could a simulation be conscious? · Watch a decision being made