By now, the term virtual reality has found its way into our everyday language and in itself does not raise serious doubts about what we are talking about when we talk about virtual reality. To experience virtual reality, we currently have to put on some kind of head-mounted display to be confronted with an “immersive, interactive, and computer-generated space” (Chalmers 2022, page 189 ). On closer inspection, however, most people would struggle to find an answer to the question of whether what we experience in virtual reality is really real, or just "real," or not real at all.

In his book Reality+, David Chalmers sets out to free us from our confusion by arguing for his main thesis and belief: Virtual reality is genuine reality. This central thesis is brought about by a rather unintuitive coupling of two main arguments. On the one hand, a large part of Chalmers' argument, which spans several hundred pages, is the simulation hypothesis. That is, the hypothesis that we have been living in a computer simulation all along, and that everything we perceive and experience is based on an artificially designed simulation (Chalmers 2022, page 29 ). On the other hand, this does not mean that we have to be global skeptics about the external world. We can still be sure that there are objects in the world around us. And technology helps us to prove this point, and to shed new light on the traditional Cartesian question of whether we can know or doubt anything other than ourselves and our consciousness. In short, it is very likely that we are sims in a simulation (so says the simulation argument). Nevertheless, the (unknown to us simulated) objects around us are still real, and we can know about them.

Throughout the book, Chalmers provides insight into a variety of traditional philosophical ideas relevant to his cause. While the text is entertaining, rich in pop cultural references, informative, and at times quite complex, it's easy to lose sight of the goal of this endeavor. But it is all connected, and somehow, I am sure, somehow the question of who deserves our worship and whether there should be such a thing as simulation theology is inherently connected to the question of whether virtual reality is real or not.

Back to the simulation argument: Statistically speaking, if perfect simulation is possible, and the vast development of technology certainly makes it seem possible in Chalmers’ view, then such perfect simulations will be created. And they will probably be created in large numbers by every intelligent population. In this way, the number of sims will soon inevitably far exceed the number of people who are not sims. By then, it's just very unlikely that we, of all people, will be the ones who aren't sims. Ergo: We are most likely sims. Assuming populations don't self-destruct before simulation technology is perfected – or other "sim blockers" thwart the plan, such as the impossibility of human-like sims, which seems "extremely speculative" (Chalmers 2022, page 101 ) from Chalmers' point of view. Ergo (still): We are most likely sims.

The good news is that it really shouldn't make a difference in our everyday lives, because virtual objects are real all the same. This simulation realism is reinforced by virtual digitalism, which says that virtual objects are digital objects (Chalmers 2022, page 194 ff. ). With digital objects, the question of realness seems less controversial and with the according hardware in mind it sounds like a no-brainer: Yes, digital objects exist, they have causal powers, they are mind-independent, non-illusory and genuine – therefore: probably real, if those are the aspects we agree on to decide on realness (Chalmers 2022, page 108 ).

After all this and more, Chalmers pulls off a final structuralist (or, more precisely, functionalist) coup. Here the key idea of structuralism (or rather functionalism) is that any scientific theory can be described in terms of structure (or rather causal roles and power, cf. (Chalmers 2022, page 428 )). If that's true, then our physical world can undoubtedly and really be reproduced structurally in a simulation. Incidentally, this is also an argument for the possibility of conscious sims. If it's all about structure, and that structure doesn't have to be substrate-dependent (i.e., necessarily made of physical brain cells), then there's no reason why consciousness couldn't be simulated. And if we can't wrap our heads around that yet, don't worry, we’ll get there eventually! Some things are substrate-independent, like a library that can be virtual and still be a real library, while other things seem to be virtual-exclusive, like a cat that is only a real cat if it is made of flesh and bones (Chalmers 2022, page 200 ). But it doesn't have to be this way, we can just wait for it to get real at some point! As simulation technology evolves, our perspective on certain things may change along the way. What doesn't seem like a real cat now will most likely be a real cat in the future, once we've gone through an appropriate conceptual shift (Chalmers 2022, page 201 ).

By now it has become clear that Reality+ (the book, not the idea) is to be placed in the field of analytic philosophy (although Chalmers himself does not tell us this until p. 370). It's all about language, it's all about how we handle concepts until they fit our purposes. And if it doesn't fit now, it will fit later, or maybe it wasn't a good concept to begin with. While Chalmers certainly provides insight into many striking thought experiments that prove the necessity of philosophical inquiry in general as well as the philosophical aspects of technology use, we unlearn reality along the way.

As consistently as he asserts that the real is not the opposite of the virtual, another juxtaposition creeps into the book without really being questioned – the virtual versus the physical: “Instead of talking about the ‘real world’, we should talk about the ‘physical world’ or the ‘nonvirtual world’” (Chalmers 2022, page 187 ). One could argue for the physicality of digital objects, for example by pointing to the hardware that comes with them, but let's just not, for now. At one point, Chalmers casually writes: “Either way, digital entities and nondigital entities are quite different things” (Chalmers 2022, page 118 ). And maybe, in the end, that’s all we needed to hear. Let them be as real as they want! They’re still different. Maybe reality is not the concept that leads us to the answer that we need.

To get to the questions in the first place, it might be worth taking a look at those virtual reality settings that can be experienced as such, where the users actively operate a headmounted display to consciously enter (and leave) an immersive, interactive and computergenerated environment. If we meet up in a virtual room to chat, to play, to make music, to simply be together in some way, we quickly realie that it’s possible. We can actually do things together, we are there together and we can have real conversations and make real friends. But it's different, right? And why is that? Will it stop being different if (big if!) we upload our minds, if we choose to actually consciously enter a perfect simulation for good (assuming we are not already in one)?

It is pretty clear that virtual reality experiences are physical experiences. On the one hand, we're physically using the technical equipment, we're moving around, there's haptic feedback from the controllers, we get something from the experience. On the other hand, in many virtual environments there is or can be a virtual body that we inhabit, that we control, that we are. This body is real. It's also obviously a different body from our physical body. And it's a body with which we can meet people. And within virtual reality, in front of a virtual other with a virtual body like mine, the question is not: are they real? but what can they do to us and what can we do to them?

If birth and death as we know them do not (yet) play a role in virtual reality, and if it is not clear that we need them to make our lives meaningful (Chalmers 2022, page 325 ), then we need to reevaluate what it means to be vulnerable in front of each other.

Bibliography