QuestionsIs the world real?A simulated world is as real as ours: every world exists through its rules
Is the world real?Virtual is real too

A simulated world is as real as ours: every world exists through its rules

The Platonic position on simulation (Moravec); every simulation is a real world

Hans Moravec born 1948Roboticist: a simulated world is a real world like any other, because a world exists through its rules, not through the machine that runs it.
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What it claims

A simulated world does not get its reality from the machine: each world is real through its own rules, and the difference with ours is only a matter of vantage point.

Why

If a world were real only through the machine containing it, ours would need another one, and so on without end.

The same idea through history
René Descartes1641Moravec starts from Descartes: a complete illusion is possible, and technology will soon make it feasible. But he draws the opposite of the sceptical hypothesis from it.
Hans Moravec1998The version presented here: a simulated world is defined by its internal rules, like ours; it is no less real because a machine runs it.
David Chalmers2003Chalmers reaches a nearby conclusion by another route: the simulation constitutes genuine physical processes.
In short

"A simulated world is as real as ours: every world exists through its rules" is an argument by Hans Moravec (Moravec, "Simulation, Consciousness, Existence", 1998, 1998) on the question "Is the world real?" (answer: virtual is real too). Its claim: A simulated world does not get its reality from the machine: each world is real through its own rules, and the difference with ours is only a matter of vantage point. According to AskPhilosophy's logic check (Z3 solver), the argument is valid only if one grants a premise the author leaves unstated (P4). AskPhilosophy presents 2 objections, 1 of them with a documented reply, and the original text behind each premise, checked word for word.

Moravec, "Simulation, Consciousness, Existence", 1998
Valid with an implicit premise

In 1998 the roboticist Hans Moravec starts from Descartes: the world we perceive could be a hoax, and virtual reality will soon make that technical. But he draws a rare conclusion. For him a simulated world is not a fake world. A simulation is defined by the internal relations among its elements (its rules), not by the machine that runs it: you can move it to a completely different computer and its inhabitants notice nothing. Our world, too, is defined by relations, which we call the laws of physics. So the difference between the physical world and a simulated one is a matter of vantage point: the physical world is the abstract world that happens to contain us. A caveat: Moravec's position goes very far (for him every interpretation of a process is a reality, even the most far-fetched), and we present only its core here.

P1A simulation is defined by its internal rules, not by the machine that runs it: if you move it to a completely different computer, its inhabitants and their mental life still follow the same simulated laws.
P2Our own world is defined the same way: by formal relationships, which we call the laws of physics.
P3If a simulated world were real only relative to the machine containing it, the same would hold for ours relative to a world containing it, and so on without end: an infinite regress.
P4 · implicit premiseAn infinite regress of this kind is not a good account of what is real: a world's reality cannot always depend on another world.
So a simulated world does not get its reality from the machine: each world is real through its own rules, and the difference with ours is only a matter of vantage point.

click a premise to reject it

If you accept every premise, logic forces you to accept the conclusion. So the debate is about the premises.
Checked by a logic solver: the premises cannot all be true while the conclusion is false.
Without the implicit premise: Without P4, the infinite regress may well be true: each world would be real only relative to a deeper world, with no starting world. Nothing in the premises rules it out.
P1 and P2 say both worlds are defined the same way, by their rules. P3 says that if a simulated world's reality depended on the machine, the same would hold for us, endlessly. P4, hidden, rejects that endless chain. So reality does not depend on the machine. What is debated: P1 (does a simulation exist without someone interpreting it?) and P4 (why reject an infinite regress?).
Analogy. A game of chess: you can play it on a wooden board, on a screen or in your head, the game stays the same, with the same possible moves and endings. It exists through its rules, not through the pieces. For Moravec, a simulated world is like that game. (Our image.)

Objections

2

Each objection is a conversation: click to see who replies and where the debate stands.

John Searle 1990 · attacks premise 1

Searle argues that computation is not a property of the physical world but of our interpretation: the wall behind him "implements" a word processor if one finds a pattern of molecule movements matching it. A simulation then has no existence of its own: it exists only for someone who interprets it.

Moravec replies
Moravec
Moravec answers critics who say a machine cannot contain a mind because its function would only be an outside interpretation. For him, the abstract relationships that make up a mind, including its own self-interpretation, exist on their own: a robot, a simulator or a book, no less than a brain, is just a way of looking at them.
The debate goes on (our summary) Moravec does not name Searle; he answers this family of critics. Searle holds precisely that syntax exists only for an observer: saying the relationships "exist on their own" is what he denies. And Moravec accepts the consequence Searle found absurd: every interpretation, even the most arbitrary, would be a reality (our summary).
Where the debate stands (our summary)Underlying disagreement: does a computation exist in the world, or only in the eye of whoever interprets it? Others, like Chalmers, seek a middle way with strict conditions for when a system implements a computation; Moravec goes all the way and makes every interpretation real (our summary).
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Gordon McCabe 2005 · attacks premise 1

McCabe argues that a digital simulation has no objective link to the system it simulates: it exists only as a physical process in the computer's parts. So nobody can live "inside" a digital simulation, and there is no simulated world that could be called real.

no reply
We have not yet found a direct reply by Moravec in the texts.
Where the debate stands (our summary)Underlying disagreement: McCabe ties a simulation to the machine that runs it; Moravec ties it to its rules, which would exist on their own. Open point (our summary).