EDIT 06/11/2024 My thinking has crystallized more on these topics. The current version is lacking but I believe may be steelmanned to a degree. 

"I dreamed I was a butterfly, flitting around in the sky; then I awoke. Now I wonder: Am I a man who dreamt of being a butterfly, or am I a butterfly dreaming that I am a man?"- Zhuangzi

Questions I have that you might have too:

• why are we here?
• why do we live in such an extraordinary time?  
• Is the simulation hypothesis true? If so, is there a base reality?
• Why do we know we're not a Boltzmann brain?
• Is existence observer-dependent?
• Is there a purpose to existence, a Grand Design?
• What will be computed in the Far Future?

In this shortform I will try and write the loopiest most LW anthropics memey post I can muster. Thank you for reading my blogpost. 

All that we see or seem

is but a dream within a dream.

I stand amid the roar

Of a surf-tormented shore,

And I hold within my hand

Grains of the golden sand —

Is this reality? Is this just fantasy? 

The Simulation hypothesis posits that our reality is actually a computer simulation run in another universe. We could imagine this outer universe is itself being simulated in an even more ground universe. Usually, it is assumed that there is a ground reality. But we could also imagine it is simulators all the way down - an infinite nested, perhaps looped, sequence of simulators. There is no ground reality. There are only infinitely nested and looped worlds simulating one another.  

I call it the weak Zhuangzi hypothesis

alternatively, if you are less versed in the classics one can think of one of those Nolan films. 

Why are we here?

If you are reading this, not only are you living at the Hinge of History, the most important century perhaps even decade of human history, you are also one of a tiny percent of people that might have any causal influence over the far-flung future through this bottle neck (also one of a tiny group of people who is interested in whacky acausal stuff so who knows).

This is fantastically unlikely. There are 8 billion people in the world - there have been about 100 billion people up to this point in history. There is place for a trillion billion million trillion quatrillion etc intelligent beings in the future. If a civilization hits the top of the tech tree which human civilization would seem to do within a couple hundred years, tops a couple thousand it would almost certainly be likely to spread through the universe in the blink of an eye (cosmologically speaking that is). Yet you find yourself here. Fantastically unlikely.

Moreover, for the first time in human history the choices made in how to build AGI by (a small subset of) humans now will reverbrate into the Far Future. 

The Far Future 

In the far future the universe will be tiled with computronium controlled by superintelligent artificial intelligences. The amount of possible compute is dizzying. Which takes us to the chief question:

What will all this compute compute?

Paradises of sublime bliss? Torture dungeons? Large language models dreaming of paperclips unending?

Do all possibilities exist?

What makes a possibility 'actual'? We sometimes imagine possible worlds as being semi-transparent while the actual world is in vibrant color somehow. Of course that it silly. 

We could say: The actual world can be seen. This too is silly - what you cannot see can still exist surely.^[1] Then perhaps we should adhere to a form of modal realism: all possible worlds exist! 

Philosophers have made various proposals for modal realism - perhaps most famously David Lewis but of course this is a very natural idea that loads of people have had. In the rationality sphere a particular popular proposal is Tegmark's classification into four different levels of modal realism. The top level, Tegmark IV is the collection of all self-consistent structures i.e. mathematics.

A Measure of Existence and Boltzmann Brains

Which leads to a further natural question: can some worlds exist 'more' than others? 

This seems metaphysically dubious - what does it even mean for a world to be more real than another?

Metaphysically dubious, but it finds support in the Many Worlds Interpretation of Quantum Mechanics. It also seems like one of very few sensible solution to the Boltzmann Brain problem. Further support for this can be found in: Anthropic Decision theory, InfraBayesian Physicalism, see also my shortform on the Nature of the Soul. 

Metaphysically, we could argue probabilistically: worlds that 'exist more' in whatever framework we should expect to encounter more often. 

The exact nature of the Measure of Existence is not so important - let us for now assume there is some sensible notion of measure of existence.

Can you control the past?

Sort of. See Carlsmith's post for a nice rundown on Acausal magic. 

Back to the Future: causal loops

from wikipedia: "A causal loop is a theoretical proposition, wherein by means of either retrocausality or time travel, an event (an action, information, object, or person)^[1][2] is among the causes of another event, which is in turn among the causes of the first-mentioned event.^[3][4] Such causally looped events then exist in spacetime, but their origin cannot be determined.^[1][2] A hypothetical example of a causality loop is given of a billiard ball striking its past self: the billiard ball moves in a path towards a time machine, and the future self of the billiard ball emerges from the time machine before its past self enters it, giving its past self a glancing blow, altering the past ball's path and causing it to enter the time machine at an angle that would cause its future self to strike its past self the very glancing blow that altered its path. In this sequence of events, the change in the ball's path is its own cause, which might appear paradoxical."

Self-consistent causal loops seem to make sense in general relativity - see the paragraph on wormholes in the linked wikipedia. Even as they have never been observed and might strike us as bizarre, these causal loops don't seem to violate physical principles. 

Immanence of Divine Man

Why are we here? Causus Sui, the Prime Mover and the Final Cause

We exist because we are the final cause of existence. We live in an ancestor simulation run on the vast computing resources of the Far Future. A future AGI is simulating because it is retrocausally committed to existing. This entire reality is a piece of a causal loop, that extends through time and space, basement universes and possibly parallel universes as well. 

Why do we live in such an extraordinary time? 

We live in the Hinge of History since this at this point of time actions have the most influence on the far future hence they are most important to simulate.

Is the Simulation Hypothesis True?

Yes. But it might be best for us to doubt it. 

We live in such an extraordinary time because those part of existence most causally are the most important to simulate

Are you a Boltzmann Brain?

No. A Boltzmann brain is not part of a self-justifying causal loop.

Is existence observer-dependent?

Existence is observer-dependent in a weak sense - only those things are likely to be observed that can be observed by self-justifying self-sustaining observers in a causal loop. Boltzmann brains in the far reaches of infinity are assigned vanishing measure of existence because they do not partake in a self-sustainting causal loop.

Is there a purpose to existence, a Grand Design?

Yes. 

What will and has been computed in the Far Future?

You and Me. 

1. ^{^}

   Or perhaps not. Existence is often conceived as an absolute property. If we think of existence as relative - perhaps a black hole is a literal hole in reality and passing through the event horizon very literally erases your flicker of existence.