1. Prologue: When the World is Not Enough

It is the year 2048. You can no longer feel your arms and legs, but you dream of the warm autumn sun breaking through colorful leaves. A blackbird calls from a distance and your daughter smiles at you, a picnic blanket, the shade of the trees. Only the flickering of the ceiling light and the flashing of the surveillance monitors bring you back to reality, and only temporarily, until the warm feeling of the pain medication makes your perception fade.

You are terminally ill. You only have a few days to live, at least that’s what the Doctor says. And yet this realization, in the bright moments between the effects of the morphine and drifting off to sleep, does not fill you with despair: you have taken precautions. Two years ago you signed a contract with AfterMath Ltd.: shortly after your death you will be scanned¹This story and most of what follows assumes that agents (at least the ones we mean here, which is ultimately supposed to include humans) can in principle be described classically, and potentially with a finite amount of classical information. This is compatible with the fact that some biological processes are genuinely quantum-mechanical and / or continuous, but a possible intuition is that these details must ultimately be irrelevant for all that matters for us as persons (including conscious experience), since robust functioning seems to forbid dependence on too fine-grained details. Whether this assumption is well-justified is the subject of contemporary debate, with a vast body of literature on e.g. the (un)suitability of “mind uploading”. For a recent proposal against this assumption, claiming that quantum states are at the heart of consciousness, see e.g. G. M. D’Ariano and F. Faggin, Hard Problem and Free Will: An Information-Theoretical Approach, in Scardigli, F. (ed.), Artificial Intelligence Versus Natural Intelligence, Springer, Cham, 2022. by a team of specially trained neuroscientists with a particular machine, and your body will be destroyed in the process. A few days later, you will be digitally resurrected in a simulated world on a computer.

You have not made this decision lightly. You have spent years studying philosophy, ethics and neuroscience. In the end, it was thoughts like Bostrom’s fable²N. Bostrom, The Fable of the Dragon-Tyrant, J. Med. Ethics 31, 273-277 (2005). and the experimental results of AfterMath that convinced you to go for it. You are pretty sure that you are trying the right thing. And you are hopeful that it will go well.

And yet, you are afraid. You are afraid because you are human. The perception fades, the pain disappears, but the fear and the will to live remain. Your eyes are closed, but you feel the Doctor enter the room. You must have heard his feet scrubbing across the plastic floor of the hospital room, albeit unconsciously.

You clear your throat. At first you can’t get a word out, but then you manage to whisper quietly.

You: “Doctor, I’m so scared…” (coughing) “I know this is not your specialty, but… I need to know! Will I really wake up in the computer simulation?”

You instantly regret having asked, because you know the doctor very well. The doctor is a former physicist, not only a physician, but a physicalist by conviction. He is excellent in his job, but you don’t remember him as particularly empathetic.

Doctor: “Hahaha, you fool! You are asking a non-question! All there is to say is that there is a human being here now, and a computer running a simulation of that thing later. This is all there is to know about the facts of the world.”

The Doctor goes on to refill your infusion. “You’ve paid AfterMath to run that computer simulation, and this is what is going to happen. I don’t even understand what you are actually uncertain about? You know exactly what will be the case in the world!”

While you’re reading: FAQ & clarifications

Q1: Is this an interpretation of quantum mechanics?
A: No. Some of it is strongly motivated by quantum mechanics, but it is a separate theory that aims at making concrete predictions for some scenarios that we do not yet understand.

Q2: What kinds of concrete predictions?
A: Probabilistic predictions for experiments that can be precisely specified, but not necessarily intersubjectively verified.
Roughly speaking, physics is currently concerned with experiments where the results can be seen and analyzed by everybody (the grey area in the picture), and algorithmic idealism’s goal is to extend this regime of applicability to all experiments, including “private” ones (blue area).

Q3: This doesn’t sound like science! What are predictions worth if nobody can check them?
A: The goal is to have a single theory that makes both types of predictions — ones that can be intersubjectively verified, and ones that cannot. If the collectively verifiable “standard” predictions work out fine (and a lot of my work on algorithmic idealism aims to show exactly that), then this is evidence for the correctness of the more exotic, private predictions.

Q4: Give me some concrete example predictions!
A: W

2. Quantum Probabilities as Objective Degrees of Epistemic Justification

To be continued.

Qx: ?
A: !