Increasingly, sophisticated computer technology obliterates the distinction between reality and imagination or artifact. In popular science reporting, for example, distinction is frequently no longer made between an actual photograph and a computer-generated graphic—which used to be (and ought to be) clearly labelled “artist’s conception.” While computer animation extends imagination, it only approximates reality in a symbolic way, sometimes even ignoring or falsely portraying basic physics. (Just think of the noisy Star Wars battles in outer space, where there is no air for sound to travel in!) Old style hand-drawn animation used to do this too, with cartoon protagonists blown up and springing back to life, or running off the edge of a cliff and only falling when they realize their precarious situation. These were gags that no one (except perhaps unsuspecting young children) took literally. They were hardly intended to be realistic.

However, the intention of virtual-reality and digital game producers, like the modern film industry, is to create ever more realistic ‘worlds’ as entertainments. This could pose a dilemma for a virtual-reality user who does not, for some reason (perhaps from spending too much time in VR) clearly understand the difference between reality and fiction. It could well be the case for young people being educated with computer graphics. Confronted with the VR producer’s intentional deceptions, how can the user be expected to know that the computer graphic or VR world is not photography or genuinely realistic?

This question recalls the doubt first expressed in modern times by Descartes and more recently by the Matrix films. The question actually has two parts, one pertaining to the VR world itself (which is a human production, like a novel or cartoon) and one pertaining to the user (who is a consumer desiring to be entertained). In terms of the former, the question is whether there are telltale signs of simulation by which an astute observer could distinguish the VR world from the real one—for example, a “glitch” in the computer program. There is, after all, a limit to the detail a simulation can provide, and there could be computer error. But as far as the effectiveness of the illusion, this limit is relative to the user’s cognitive capacities, which are also limited. The user must, on some basis, be able to tell the difference, which brings us to the other part of the question.

The user is a biological organism who lives in the real physical world, but enters the VR world as into a game, voluntarily and often with other players, like entering on stage with other actors. There is a conditional willing suspension of disbelief, which in traditional entertainment is asked primarily of a passive audience. Unlike readers of a novel or the theater audience for a play, the VR user is both actor and audience. A literal online game can be interactive with other real players, who have a life outside the game—offstage, so to speak. It also provides a virtual world with which to interact, which includes other human or non-human figures that are not actual players. These non-players are not conscious subjects but fictions in the VR, defined by the program as part of the stage sets. (Digital animation allows the “stage” to be dynamic, constantly changing.) While the non-players are not simple cardboard cut-outs, they are no more than part of that programmed dynamic stage set. Therein lies a key difference between real human beings (or creatures) and simulated ones. Real agents have their own agency; simulated agents are fictions that express only the agency of the real people who create the program.

The VR user is a player in a virtual-reality—a real person who chooses to engage with the VR in order to have a certain kind of experience. This player—call her P—may or may not be represented in the virtual ‘world’ by an avatar. (As P, you could be seeing yourself as a character in the story, but in any case you are seeing the VR world through your own real eyes.) Since it is provided by a computer program that is necessarily finite, the virtual world is necessarily limited, furnishing only a finite variety of possible inputs to P’s senses. In principle, that is a key difference between the VR world and the real world, corresponding to a fundamental difference between artifacts and natural found things.

However, the situation is actually similar for ordinary experience by real people in the real world. The human nervous system only processes finite information, from which it fabricates the natural illusion of an external world. The difference between natural input of the senses and the input of VR is only relative. We know that the VR is not real when we know that we are wearing a VR headset or some such thing. For the illusion of a virtual reality to be complete (as in The Matrix), no such clue must be available. P must be unaware of the deception and unable to recall entering the VR world from an existence outside it.

That conceivable possibility brings us to another contemporary confusion, expressed provocatively in the rhetorical question: “Are you living in a simulation?” Suppose you simply find yourself (like Descartes, or Neo in the The Matrix?) in a world whose reality you doubt. After all, if somehow you cannot tell the difference between simulation and reality, you might have been born and raised within a simulated world instead of the supposedly “real” one, and not be the wiser for it. Even a memory you seem to have of childhood—or of putting on VR goggles—could be merely a simulated memory, part of the VR program. However, this doubt confounds the notions of player and non-player; the difference between them is glossed over in the so-called Simulation Argument (that we are “probably living in a simulation”).

By assumption, P is a live embodied human who lives in the real world, in which the VR is a program running on a real computer, created by real programmers. By definition, P is not part of the program and P’s memories are not part of the stage set, so to speak. The fact that the VR world is convincing to P does not imply that P is “living” in it rather than in reality. (Much less does it imply that there is no reality, only a nested set of illusory worlds within worlds!) It implies only that P, at that moment, is unable to discern the difference—and that to doubt the reality of the world is to doubt one’s own reality.

Another player (or P at another time) might be able to tell the difference. And even if P could happen to be right about actually living in a simulation, there would necessarily be a real world in which that simulation is maintained in a real computer. But P cannot be right, given premises of the situation: namely, that there is a fundamental difference between a player and a non-player, and that P happens to be a player rather than a mere prop. For P to be right about “living” in a simulation that includes what appear to be other conscious players, simulated players (including P herself) must be possible. This is a separate and nonsensical idea. For P to “live” in a simulation at all means that P is an element of the simulation, not someone real from outside it. Then P is not a player after all, but a non-player—a prop, with a simulated brain and body supposedly able to produce the simulated consciousness necessary for “living” in the simulation. If there are other seeming players in P’s world, then their brains and bodies would also have to be effectively simulated. Recursively, there would be simulated players in the world of each simulated player, each with simulated players in their world, ad infinitum. This might seem logically possible, but it would require infinite computation and zero common sense.

There is a difference between a simulation that can fool a real subject and a simulation that is intended to be an artificial subject—such as a real-world emulation of the brain. They are both artifacts, and any artifact is a finite well-defined product of human definition and ingenuity. A simulation is an artifact that attempts to exhaust the reality of a natural thing or process (such as the brain or a real environment). It cannot truly do so, since it is only finitely complex, while natural reality may be indefinitely complex. So, two quite different questions arise: (1) is the simulation detailed enough to fool a conscious subject who wishes to be entertained? And (2) is the simulation (of the brain) complex enough to be an artificial subject who is conscious?

Of course, no one can experience another person’s consciousness. (That seems to be part of what it means to be an individual.) So, to verify that a simulated brain “is conscious” can only involve behavioral tests. Such a test could include simply asking it whether it is conscious. Yet, it could have been programmed to answer yes, in effect lying. (‘No’ would be a more interesting answer. That too could have been programmed, ironically honest. On the other hand, it might reflect a sense of humor—suggesting, though not proving, consciousness.) Turing’s solution was entirely pragmatic: if it acts enough like a conscious being then we may as well treat it as one. However, applied to doubt about whether one is living in a simulation, Turing’s solution would be unsatisfying: if you cannot tell the difference, then for you there is no difference. But for the beings trapped in the Matrix, the difference certainly mattered. For children learning about the real world, even relatively realistic simulation may provide bad education.