Lecture 13: reality

• are we living in a simulation?
  (Nick Bostrom)
• the Dust Hypothesis
  (from Greg Egan's Permutation City)

we are living in a simulation, or else... likely nobody ever will (Nick Bostrom): ABSTRACT. This paper argues that at least one of the following propositions is true:

1. the human species is very likely to go extinct before reaching a "posthuman" stage;
2. any posthuman civilization is extremely unlikely to run a significant number of simulations of their evolutionary history (or variations thereof);
3. we are almost certainly living in a computer simulation.

It follows that the belief that there is a significant chance that we will one day become posthumans who run ancestor-simulations is false, unless we are currently living in a simulation.

we are living in a simulation, or else... likely nobody ever will (Nick Bostrom): ABSTRACT. This paper argues that at least one of the following propositions is true:

1. the human species is very likely to go extinct before reaching a "posthuman" stage;
2. any posthuman civilization is extremely unlikely to run a significant number of simulations of their evolutionary history (or variations thereof);
3. we are almost certainly living in a computer simulation.

It follows that the belief that there is a significant chance that we will one day become posthumans who run ancestor-simulations is false, unless we are currently living^* in a simulation.

---

^* 'Ah, I understand . . .' the master said, glancing around, 'you've killed us, we're dead. Oh, how intelligent that is! And how timely! Now I understand everything.'
   'Oh, for pity's sake,' replied Azazello, 'is it you I hear talking? Your friend calls you a master, you can think, so how can you be dead? Is it necessary, in order to consider yourself alive, to sit in a basement and dress yourself in a shirt and hospital drawers? It's ridiculous! . . .'
   [from The Master and Margarita by Mikhail Bulgakov]

slide 3

preliminaries

multiple realizability of cognition

"We need only the weaker assumption that it would suffice for the generation of subjective experiences that the computational processes of a human brain are structurally replicated in suitably fine-grained detail, such as on the level of individual synapses. This attenuated version of substrate-independence is quite widely accepted."

the technological limits of computation

• available computing power
• computation required for simulating/emulating the brain
• simulating the environment

---

"Posthuman civilizations would have enough computing power to run hugely many ancestor-simulations even while using only a tiny fraction of their resources for that purpose."

slide 4

the core simulation argument

The basic idea of this paper can be expressed roughly as follows:

If there were a substantial chance that our civilization will ever get to the posthuman stage and run many ancestor-simulations, then how come you are not living in such a simulation?

slide 5

the core simulation argument (Bostrom)

slide 6

an analogous situation of a more familiar kind

"Suppose that x% of the population has a certain genetic sequence S within the part of their DNA commonly designated as 'junk DNA'. Suppose, further, that there are no manifestations of S (short of what would turn up in a gene assay) and that there are no known correlations between having S and any observable characteristic.

Then, quite clearly, unless you have had your DNA sequenced, it is rational to assign a credence of x% to the hypothesis that you have S. And this is so quite irrespective of the fact that the people who have S have qualitatively different minds and experiences from the people who don't have S. (They are different simply because all humans have different experiences from one another, not because of any known link between S and what kind of experiences one has.)"

slide 7

implications

"The possibility expressed by alternative (3) is the conceptually most intriguing one. If we are living in a simulation, then the cosmos that we are observing is just a tiny piece of the totality of physical existence. The physics in the universe where the computer is situated that is running the simulation may or may not resemble the physics of the world that we observe. While the world we see is in some sense 'real', it is not located at the fundamental level of reality."

---

1. humans are likely to go extinct before going "posthuman"
2. posthumans are likely to be averse to ancestor simulation
3. we are likely to be living in a simulation

slide 8

implications

"The possibility expressed by alternative (3) is the conceptually most intriguing one. If we are living in a simulation, then the cosmos that we are observing is just a tiny piece of the totality of physical existence. The physics in the universe where the computer is situated that is running the simulation may or may not resemble the physics of the world that we observe. While the world we see is in some sense 'real', it is not located at the fundamental level of reality."

why care?

From a short story, "The Janitor on Mars", by Martin Amis:

"...The War with the Scythers of the Orion Spur was hotly prosecuted for just over a billion years. Who won? We did. They're still there, the Scythers. Their planet is still there. The nature of war changed, during that trillennium. It was no longer nuclear or quantum-gravitational. It was neurological. Informational. Life goes on for the Scythers, but its quality has been subtly reduced. We fixed it so that they think they're simulations in a deterministic computer universe. It is believed that this is the maximum suffering you can visit on a type-V world."

slide 9

implications

"Further rumination on these themes could climax in a naturalistic theogony that would study the structure of this hierarchy, and the constraints imposed on its inhabitants by the possibility that their actions on their own level may affect the treatment they receive from dwellers of deeper levels.

For example, if nobody can be sure that they are at the basement-level, then everybody would have to consider the possibility that their actions will be rewarded or punished, based perhaps on moral criteria, by their simulators. An afterlife would be a real possibility.

Because of this fundamental uncertainty, even the basement civilization may have a reason to behave ethically. The fact that it has such a reason for moral behavior would of course add to everybody else's reason for behaving morally, and so on, in truly virtuous circle. One might get a kind of universal ethical imperative, which it would be in everybody's self-interest to obey, as it were 'from nowhere'."

slide 10

implications

"Supposing we live in a simulation, what are the implications for us humans? The foregoing remarks notwithstanding, the implications are not all that radical. Our best guide to how our posthuman creators have chosen to set up our world is the standard empirical study of the universe we see. The revisions to most parts of our belief networks would be rather slight and subtle — in proportion to our lack of confidence in our ability to understand the ways of posthumans.

Properly understood, therefore, the truth of (3) should have no tendency to make us 'go crazy' or to prevent us from going about our business and making plans and predictions for tomorrow. The chief empirical importance of (3) at the current time seems to lie in its role in the tripartite conclusion established above. We may hope that (3) is true since that would decrease the probability of (1), although if computational constraints make it likely that simulators would terminate a simulation before it reaches a posthuman level, then out best hope would be that (2) is true."

---

1. humans are likely to go extinct before going "posthuman"
2. posthumans are likely to be averse to ancestor simulation
3. we are likely to be living in a simulation

slide 11

Bostrom's argument: a summary

"If (1) is true, then we will almost certainly go extinct before reaching posthumanity. If (2) is true, then there must be a strong convergence among the courses of advanced civilizations so that virtually none contains any relatively wealthy individuals who desire to run ancestor-simulations and are free to do so. If (3) is true, then we almost certainly live in a simulation. In the dark forest^* of our current ignorance, it seems sensible to apportion one's credence roughly evenly between (1), (2), and (3)."

---

Nel mezzo del cammin di nostra vita
mi ritrovai per una ^*selva oscura
ché la via diritta era smaritta.

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1. humans are likely to go extinct before going "posthuman"
2. posthumans are likely to be averse to ancestor simulation
3. we are likely to be living in a simulation

slide 12

an interlude: the concept of Demiourgos

• the Problem of Evil
• the Demiourgos:
  "The term Demiurge (or Yaldabaoth, Yao, Bythos and several other variants, such as Ptahil used in Mandaeanism) refers in some belief systems to a deity responsible for the creation of the physical universe and the physical aspect of humanity." [Wikipedia]
• Gnostic Christianity (the Nag Hammadi corpus)
• the Gnosticism of Philip K. Dick

slide 13

Greg Egan on the nature of Copy consciousness

"For any human, absolute proof of Copy sentience was impossible. For any Copy, the truth was self-evident: cogito ergo sum. End of discussion.

There were questions about the nature of this [...] condition which the existence of Copies illuminated more starkly than anything which had come before them. Questions which needed to be explored before the human race could confidently begin to bequeath its culture, its memories, its purpose and identity, to its successors.

Questions which only a Copy could answer."

[Permutation City, p.45]

Experiment 1

• trial 0: time resolution 1ms.
• trial 1: time resolution 5ms.
• trial 2: time resolution 10ms.
• ...
• trial 7: time resolution 10000ms.

"What am I? The data? The process that generates it? The relationships between the numbers? All of the above?" [p.47]

"And if the computations behind all this had been performed over millennia, by people flicking abacus beads, would he have felt exactly the same?

It was outrageous to admit it — but the answer had to be yes."

slide 15

Experiment 2

trial 1: reverse order [p.78] trial 2: odd-numbered states, then even. trial 3: pseudo-random ordering of states.
	6accdae13eff7i3l9n4o4qrr4s8t12ux	data aequatione quotcunque fluentes quantitates involvente, fluxiones invenire et vice versa

slide 16

Experiment 2

trial 1: reverse order [p.78] trial 2: odd-numbered states, then even. trial 3: pseudo-random ordering of states.
	6accdae13eff7i3l9n4o4qrr4s8t12ux	data aequatione quotcunque fluentes quantitates involvente, fluxiones invenire et vice versa

slide 17

Experiment 2

• trial 1: reverse order [p.78]
• trial 2: odd-numbered states, then even.
• trial 3: pseudo-random ordering of states.

---

"Now he was ... dust. To an outside observer, these ten seconds had been grouped up into ten thousand uncorrelated moments and scattered through real time — and in model time, the outside world suffered an equivalent fate. Yet the pattern of his awareness remained perfectly intact: somehow he found himself, 'assembled himself' from these scrambled fragments. He'd been taken apart like a jigsaw puzzle — but his dissection and shuffling were transparent to him. Somehow — on their own terms — the pieces remained connected." [p.80]

slide 18

Experiment 3

• trial 0: same geographic location. [p.131]
• trial 1: 500 processor clusters, distributed globally.
• trial 2: 1000 processor clusters, distributed globally.
• trial 3: 50 sections, 20 time sets, distributed over 1000 clusters.
• trial 4: 50 sections, 20 time sets, randomly allocated over 1000 clusters.

"Paul stopped counting, stretched his arms wide, stood up slowly. He wheeled around once, to examine the room, checking that it was still intact, still complete. Then he whispered, 'This is dust. All dust. This room, this moment is scattered across the planet, scattered across five hundred seconds or more — but it still holds itself together. Don't you see what that means?'" [p.133]

slide 19

implications?

"The whole idea of a creator tears itself apart. A universe with conscious beings either finds itself in the dust... or it doesn't. It either makes sense of itself on its own terms, as a self-contained whole ... or not at all. There never can, and never will be, Gods."

[p.338]

slide 20

And yet, and yet... Denying temporal succession, denying the self, denying the astronomical universe, are obvious acts of desperation and secret consolation. Our fate (unlike the hell of Swedenborg or the hell of Tibetan mythology) is not frightful because it is unreal; it is frightful because it is irreversible and ironclad. Time is the thing I am made of. Time is a river that sweeps me along, but I am the river; it is a tiger that tears me apart, but I am the tiger; it is a fire that consumes me, but I am the fire. The world, unfortunately, is real; I, unfortunately, am Borges.

Friend, this is enough. Should you wish to read more
Go and yourself become the writing, yourself the essence.

---

And yet, and yet... Negar la sucesión temporal, negar el yo, negar el universo astronómico, son desesperaciones aparentes y consuelos secretos. Nuestro destino (a diferencia del infierno de Swedenborg y del infierno de la mitología tibetana) no es espan toso por irreal; es espantoso porque es irreversible y de hierro. El tiempo es la sustancia de que estoy hecho. El tiempo es un río que me arrebata, pero yo soy el río; es un tigre que me destroza, pero yo soy el tigre; es un fuego que me consume, pero yo soy el fuego. El mundo, desgraciadamente, es real; yo, desgraciadamente, soy Borges.

Freund, es ist auch genug. Im Fall du mehr willst lesen,
So geh und werde selbst die Schrift und selbst das Wesen.

(Angelus Silesius: Cherubinischer Wandersmann, VI, 263. 1675).

Jorge Luis Borges, Nueva Refutación Del Tiempo

the end