Are we living in a simulation?

The short answer, and I think that there is such an answer would be difficult to dispute, is unequivocally "yes!" Each one of us, unless we are currently in a deep sleep or in a coma, is going around with a simulation inside their head right now, including me as I write this post. 

But what exactly do I mean by that?

The complete answer is both simpler than it appears, and more complex. In 2001, during the height of the first wave of what might tentatively be referred to as "post-millenial techno-boosterism", Nick Bostrom published a seminal paper entitled "Are you living in a computer simulation?" An expanded and revised version of this popular and influential thought experiment was subsequently published in 2003 in the journal Philosophical Quarterly. (The somewhat unusual choice of pronoun in the title, "you", is, one is tempted to assume, a not-so-subtle appeal to the superior technological resources of the architects of said simulation, the ostensibly superior intellectual capacity of the paper's author, or both, in comparison with the assumed capabilities of the reader, in addition to its obvious appeal as a rhetorical device).

So what exactly was I saying when I answered so confidently in the affirmative just now in response to this admittedly radical notion? Well, this part is actually quite simple. My simulation, and presumably yours as well, is nothing more nor less than the world as it is presented to us by our individual brains at any given moment. 

There! Satisfied? 

It's ok if you're not. But let us continue.

Perhaps a much more interesting if slightly more intractable question is this: If it is true that some of us are living in a simulation functionally distinct from the one most of us seem to be living in already, how do we know which people are living in which simulation(s)? Or is possible that we all might be living in the SAME "alternative" simulation? Quite unlike the first problem, the response to these considerations is not immediately clear. Part of the trouble, as is so often the case, has to do with the ambiguities of language. What do we really mean when we ask, "do you (or I, or anybody else in particular) live in a simulation?"

The very wording of the question seems to suggest, indeed assume, at least two things:

1.)  There exists some difference between someone who lives in a simulation and someone who doesn't.

2.)  That some of us might live in a simulation, while others do not.

And, possibly also

3.)  That if it is true that at least some of us live in a simulation, the functional characteristics of each alternative simulation are next to identical, whatever their method of implementation.

For a start, it's worth pointing out that there is no known criterion upon which, even in principle, one could distinguish someone living in a simulation from someone who supposedly isn't. All phenomenal or experiential states have at least that in common: that they involve some kind of experience. So using, for instance, something akin to the principle of the identity of indiscernibles, in addition to the fact that we already appear to be embedded in a biological simulation, we might reasonably conclude that assumption (1) is either false or incoherent. Additionally at the present time there is no part of the body, brain or otherwise, that is known to confer the ability to exist, or not, in an alternative simulation of the type proposed in the original thought experiment. After all, as far as we know, every brain we might encounter works in an essentially similar way; unless, of course, we suffer injury or damage as the result of a stroke, or by virtue of a genetic or developmental abnormality. And even in those cases, the basic capacity to experience a phenomenal state of one sort or another tends to remain robust. This, along with the aforementioned improbability of (1), would seem to cast considerable doubt on the practical feasibility of (2). Bostrom handles this by simply assuming, without evidence, that a richly detailed simulation essentially indistinguishable from that produced by our nervous systems could be implemented using some type of alternative hardware, the detailed workings of which have yet to be described. 

Finally, as regards assumption (3), because no mechanism has been proposed by which any alternative simulation might be implemented in such a way that would render it functionally identical with those of our native biology, or indeed those of other discrete simulations, there is no way to know how many of these alternative simulations might be active at any given time, nor any way to determine whether we may or may not be living in one giant "meta-simulation" in which every human being, possibly even other animals as well, take part, or whether only certain groups of humans are actually living in simulations, either as isolated individuals or as component parts of aggregate simulations. So far, the human nervous system is the only structure we've discovered in the entire universe that is capable of implementing, as Bostrom puts it, "human-type experiences." Not even our most advanced artificial intelligence systems have come anywhere close to achieving that which is readily achieved without any effort by ordinary human beings.

An additional complication arises when one considers that the entities responsible for creating or maintaining the proposed alternative simulations, whether human or some other type of being, could themselves be the products of other simulations. If it's "turtles all the way down", there is simply no end to the potential inconsistencies that would be likely to arise regarding such apparently basic features of our universe such as causality, the arrow of time, the historical development of languages and culture, and so on. It would appear unlikely that, given such a vast array of simulaneously active simulations operating on multiple levels, that anything so seemingly coherent as, for instance, the fossil record left behind by the evolution of our early hominid ancestors could have come about by means of an ad-hoc sequence of nested simulations being run at some unspecified date (or dates) far in the future. It's telling that Bostrom devotes a great deal of space in his paper to speculating on the mechanics of "post-human civilizations", but none whatsoever regarding the unavoidably messy historical ramifications of the hypothesis were it actually to be confirmed. 

This brings us to another important point of clarification that must finally be addressed before we can really begin to make sense of the problem at issue: What exactly do we mean by "simulation"? Clearly, the kind of simulation I referred to at the outset of this digression, the simulation on the level of the individual presumed to be generated by the brain, is avowedly NOT the type of simulation referred to in the original thought experiment. What Bostrom had in mind was something very different; something, you might even say, far more sinister. What he obviously meant was that some ill-defined group of human beings might be living in a sort of collective delusion, a fundamental deception regarding the nature of "reality", the supposedly "objective" reality that we hold in common: the type of deception depicted, to pick a prominent example, in the movie "The Matrix": 

 

To put it in a slightly more formal way, the original question is presented as an example of a particular species of radically skeptical assertion about the fundamental nature of the world as it is experienced by human beings. There is a marked similarity in the spirit of the proposal with another radically skeptical thought experiment from the philosophical literature: Descartes' evil demon. In a much-quoted passage, Descartes asked if it was possible that some malign entity or "demon" could be systematically deceiving him as to his fundamental convictions regarding his perceptions of the properties of the external world; that there is such a world outside himself, that his perceptions provide a reliable guide to the various properties of that world, and so on, even regarding the existence of his own body. Or, as Descartes himself put it, 

"I shall think that the sky, the air, the earth, colors, shapes, sounds and all external things are merely the delusions of dreams which he has devised to ensnare my judgement. I shall consider myself as not having hands or eyes, or flesh, or blood or senses, but as falsely believing that I have all these things."  

                - René Descartes, Meditations on First Philosophy 

Many other examples of radically skeptical arguments are to be found throughout history, from Zhuangzi to Nagarjuna to Plato's Cave. The trouble is that whereas philosophers like these often made effective use of such devices as footholds in order to scale further philosophical heights, Bostrom seems rather disturbingly committed to the actual truth of his proposition. While he does refrain from arguing directly that anyone IS living in a simulation at any point in the paper, you could certainly be forgiven for coming to precisely that conclusion over the course of the entire argument! In fact the intensely probabilistic approach employed in support of his premise could almost be viewed as a kind of "smokescreen" for what might easily be interpreted as a strong desire on the part of the author that the truth of the notion somehow obtains. 

In short, it appears Bostrom and many of his followers really believe their own brand of b.s., a rather untenable position in the service of advancing a supposedly "skeptical" argument. Indeed, it may prove ultimately rather difficult to defend the assertion that the so-called "simulation hypothesis" is a species of skeptical argument, resting, as it does, on so many unjustified beliefs and unproveable assumptions. The more one examines the issue, the more it actually begins to resemble an exercise not in skepticism, but rather in credulous optimism about the future capabilities of advanced societies and high technology. 

And despite the fact that Bostrom himself is not a physicist, it is also, I believe, a good example of a particular type of cognitive bias that many contemporary physical scientists tend to exhibit in their thinking about matters philosophical, a bias which both tends to distort their thinking in ways that fly in the face of sound reasoning and often causes them to, as it were, "reinvent the wheel" and attempt to take philosophical ideas already extant out of context in order to reformulate them in ways that are compatible with whatever postition or idea they wish to promote, no matter how implausible.

This last point is a theme which I will no doubt revisit in subsequent posts, so watch for that. And of course, feel free to comment as I realize this is still an ongoing debate, and not one that is likely to be definitively resolved any time soon! I'd be interested to hear what you have to say.