Reality+: Virtual Worlds and the Problems of Philosophy

by David J. Chalmers

That’s the Eleatic dictum: to be real is to have causal powers.

That is, something exists if and only if it can affect things or b...

As a result, anything that falls under Berkeley’s dictum also falls under the Eleatic dictum.

Santa Claus does not fall under the Eleatic dictum.

not in this universe

Santa has no causal powers: He doesn’t make a difference in the world. According to stories about Santa Claus, Santa has enormous causal powers: He delivers billions of Christmas presents in a single night. But those stories are false; Santa has no intrinsic causal powers. Of course, the stories themselves have causal powers. They affect cards and costumes and children through...

The Eleatic dictum isn’t the whole truth about reality. There could be real things that have no causal powers. Maybe numbers are real without having causal powers, for example. Maybe there could be a forgotten dream with no causal powers. But causal powers provide at least a sufficient condition for reality. If something has causal powers, then it exists and it is real. In this way, c...

Reality as mind-inde...

Philip K. Dick in his 1980 short story “I Hope I Sh...

“Reality is that which, when you stop believing in it, doesn’t go away.” The idea is that if no one believed in Santa Claus, Santa Claus would not be on the scene, but if no one...

I don’t think Dick’s dictum is quite right as it stands. If we stop believing in Gandalf but still see him on screen, he doesn’t go away. That doesn’t mean that Gandalf is real. The same goes for illusions and hallucinations: even if I belie...

Still, Dick is onto something. In those cases, the presence of Gandalf or the mirage still depends on people’s minds—their thoughts and experiences. If no one had ever thought about Gandalf, he would never have entered our lives. If we stop experiencing the mirage, it will go away. So we might say, “Reality is that which, when it’s not in anyone’s mind, doesn’t go away.” Or maybe better: “Reality is that which doesn’t depend on anyone’s mind for its existence.”

don’t sims need our thought/mind for their existence?

counterpoint is what we might call Dumbledore’s dictum, spoken by Hogwarts headmaster Albus Dumbledore toward the end of the Harry Potter series: “Of course it is happening inside your head, Harry, but why on earth should that mean that it is not real?” Your thoughts and experience happen inside your head and depend on your mind, but they’re real all the same. Social entities like money also depend on people’s minds. If no one regarded dollar bills as valuable, they wouldn’t be money—but money is real all the same.

Still, mind-independence can serve as a useful sufficient condition for being real, and one that helps to explain at least one useful dimension of our sense of reality. If something exists in a way that’s independent of anyone’s mind, then it has an especially robust sort of reality. If something exists only in a way that depends on our minds, then it’s less robustly part of the external world.

so sims are less robustly part of the external world?

Reality as non-illusoriness.

What is the difference between illusio...

So far, we’ve asked the question, “Do things...

Another crucial question, however, is “Are things as they seem?” We can use this question as a f...

That is, something is real when it’s the...

Something is illusory when it’s not the...

Physical reality is real because it’s roughly the way it seems. When it seems that there’s a ball in front of you in physical reality, there’s typically a ball there. According to the standard view, virtual reality isn’t real because it isn’t the way it seems. In VR it seems that there’s a ball there, but there’s not. In virtual reality, the story goes, things are not as they seem—that is, virtual reality is an illusion. Right now, it seems to me that I’m sitting in a chair, using a desktop computer, in a house somewhere in the Hudson Valley. It seems to me that there’s an algae-covered pond outside the window, with geese wandering around. It seems to me that I’m a philosopher working on a book on reality. It seems to me that I grew up in Australia and that I now live in New York. All this and more constitutes what we might think of as my apparent reality. This apparent reality is real if, and only if, things are as they seem. If I’m really sitting in a chair, and there is really a pond outside the...

Of course, I can be wrong about some things—maybe those aren’t really geese outside the window—without my reality collapsing. But if I’m wrong about almost everything, then it’s reas...

What counts as the way th...

There’s more than one candidate. There’s the way we perceive things to...

There’s also the way we believe things to be, using our thinking and reasoning as well as perception. I can perceive a pink eleph...

I can believe that there was a Big Bang without hav...

what if our belief ends up being incorrect when evidence is revealed?

where simulation realism is concerned, I’ll understand the fourth criterion as saying things are real when they’re roughly as we believe them to be.

Reality as genuineness.

we cannot just say of something that it is real. If we did, it would invite the question “A real what?” The issue would have to be whether it is a real diamond (as opposed to a fake diamond), or a real duck (as opposed to a decoy duck). We might call this Austin’s dictum: Instead of asking whether something is real, ask whether it’s a real X.

I don’t think Austin’s dictum is quite right. It’s perfectly reasonable for a child to ask whether Santa Claus is real or whether the Easter Bunny is real. You could ask whether the Easter Bunny is a real rabbit, or a real spirit, or whatever. But there’s also a question you can ask while staying neutral on whether it’s a rabbit or a spirit: Is the Easter Bunny real? That is, does it really exist? The answer seems to be no. It’s a folkloric figure that has been passed down for generations; the folklore is real, but the bunny is not.

maybe in this universe

The Easter Bunny doesn’t really exist, it doesn’t have causal powers, and it isn’t independent of our minds.

in this universe

Still, Austin’s dictum captures something crucial. We often don’t just want to know whether something is real; we want to know whether it’s real money or a real iPhone. If someone gives me an object that looks like a Rolex watch, the object is indisputably real. It’s a real thing, at least. What I’m interested in is whether it’s a real watch, and in particular whether it’s a real Rolex. We could put this by asking whether the watch is genuine—that is, is it a genuine watch? Is it a genuine Rolex? The same goes for life in a simulation.

It’s one question to ask whether buildings and trees and animals we’re seeing are real; perhaps someone could be convinced that they’re real digital entities. But it’s another question to ask whether they’re real buildings, real trees, and real animals. If they’re real objects but not real buildings, then things are not as they seem. So when something see...

Is simulated real...

Does it really exist? Does it have causal powers? Is it independent of our minds? Is it as it seems? Is it a genuine X?

These five criteria—existence, causal powers, mind-independence, non-illusoriness, and genuineness—

None of these criteria for reality make it easy to figure out what’s real; they just clarify the question a little.

If we’re in a perfect simulation, is our world real?

Do the objects we perceive in this simulated world really exist?

If I’m in a perfect simulation, does the tree outside my window really exist? My opponent says, “No, the tree and the window itself are mere hallucinations.” I say, “Yes, the tree and the window really exist.”

At some level they’re digital objects, grounded in digital processes in a computer, but the...

The second criterion asks: Do the objects we perceive h...

Do they make a difference? My opponent says “No, the tree merely seems to make a difference.” I say, “Yes, the tree is a digital object with many causal powers.” It produces leaves (which are themselves digital objects), it supports (digital) bird...

The third criterion asks: Are the objects we perceive indep...

If minds go away, can they still exist? My opponent says, “No, the tree I perceive exists only in my mind, and if we all went away, it wouldn’t exist.” I say, “Yes. The tree is a digital object, which does not depend on me for its existence.” Even if all (simulated and unsimulated) human life went away, in principle the tree could continue to exist as a digital object.

what if you turn off/on simulation? does it exist if it’s powered down? the digital bits are still stored somewhere until deleted.

The fourth criterion asks: Are things as they seem to be?

Are flowers really blooming in my garden, as they seem to be? Am I really a philosopher from Australia, as I seem to be? My opponent says, “No, these are mere illusions, and in reality there are no flowers and no Australia.” I say, “Yes, there are really flowers blooming in the garden, and I am really from Australia.” If my whole world is a simulation, flowers are ultimately digital objects, and Austral...

The fifth criterion asks: Are the things I experience in a simulation real flowers, and r...

My opponent says, “No. Even if they’re real digital objects, these objects are at best fake flowers, not real flowers.” I say, “Yes, these objects are real flowers, the books are real books, and the people are real people.” If I’ve lived my whole life in a s...

“If we’re in a perfect simulation, the objects around us are real and not an illusion.” The reference to illusion puts the greatest weight on the fourth criterion: Simulation realism holds that things are largely as we believe them to be. Now, we believe that cats exist, and that cats do things, and that they are real cats. Simulation realism entails that in a simulation, these beliefs are largely true.

Perhaps things would go differently if we defined reality as fundamentality or originality.