Are we living in a simulation? Is there anyway to know we're not? The answer might not be completely reassuring, but we don't have to give up on knowledge altogether, writes Anandi Hattiangadi. 

It is the year 4000CE, and there are no trees, no birds, and no humans. The Earth has been taken over by artificial superintelligences (ASIs), who vastly exceed humans in their computational capacity. These beings have destroyed us along with most organic matter on the planet in pursuit of the materials and power needed for their existence. Though they care little for the natural world, the ASI’s pursuit of knowledge is rapacious. In order to understand their history, they have developed a computer simulation, much like the simulated world depicted in the film, The Matrix, but which is a perfect computational model of the universe down to the smallest subatomic particle, and from the very moment of the big bang. As the program runs, virtual organisms evolve, from virtual amoebae to virtual dinosaurs, and ultimately, virtual humans—one of whom is just like you. Virtual-you enjoys all of your sensory experiences and thoughts. Virtual-you interacts with virtual friends and family who are indistinguishable from yours. And virtual-you lives in a virtual world that is an exact, digital replica of your world, in every microphysical detail. In fact, virtual-you is reading this article right now. Are you virtual-you?

“Of course not!”, you say. “The scenario just described is fantastical and highly unlikely to be true.” However, a growing number of philosophers, scientists, and forecasters have been taking seriously the possibility that rapidly accelerating progress in artificial intelligence and robotics will lead to a ‘technological singularity’, an ‘intelligence explosion’ from which super intelligent beings will emerge who are capable of both destroying us and creating powerful, complex digital worlds. Elon Musk called AI humanity’s “biggest existential threat”, while Oxford’s Nick Boström has argued that it is highly likely that we are virtual beings existing in a computer simulation. A crucial assumption of Boström’s argument is that your conscious experiences and thoughts can be realized in a substrate quite different from a human brain; that your mind could be ‘uploaded’ to a powerful enough computer. Though controversial, this assumption is nevertheless plausible. For instance, we are drawn to viewing the character Ava in the film Ex-Machina as possessing a conscious mind, though her mind is realized in a silicone brain.

Since your sensory experience does not rule out the possibility that you live in a computer simulation, she argues, you don’t know that you don’t live in one.

Moreover, even if it is unlikely that the scenario described above is true, the mere possibility that it is true that should give you pause, because it gives rise to a skeptical argument that calls into question whether you know many of the ordinary things that you think you know: that you have a body, that there are birds and trees, that your friends and family exist, and so forth.

The skeptical argument goes as follows. First, the skeptic points out that if you do know that you have a body, you can deduce and thereby come to know that you don’t live in a computer simulation. This is based on the plausible thought that you can always learn something new by competently deducing it from what you already know. Since the statement that you are not living in a computer simulation follows from the statement that you have a body, you can come to know the former by deducing it from the latter.