I don’t want to freak you out here, but there’s a chance you’re not the only 'you' in existence.

I'm not talking about the possibility that you might actually have two different brains, which means it’s virtually impossible to tell which one is 'you'. I’m talking about the fact that there could well be countless parallel universes, and each one contains a slightly different version of you.

Within that parallel universe construct, our own reality might not be as 'real' as you think. Are some of the most massive objects in our Universe nothing but holograms? Is our Universe itself a hologram? Is this whole thing one giant simulation and we’re just characters in the most advanced video game ever?

I swear I’m not high. Everything I just mentioned is part of actual thought experiments that have been devised and debated over by the world’s best thinkers for years now, because one way or another, we have to make sense of this very strange and incredibly unlikely reality we’ve found ourselves in.

At Recode's annual Code Conference this week in California, billionaire tech genius Elon Musk was asked about the possibility of us humans being unwitting participants in a giant simulation built by some alien civilisation that’s far more advanced than our own.

His argument is pretty simple, if we look at our own history of video games. Forty years ago, video games meant stuff like Pong and Space Invaders. Now we have photorealistic, three-dimensional stuff that looks like this, and we could have millions, potentially even billions, of people all playing the same game online at the same time.

Sure, there’s a certain 'uncanny valley' quality to our video game counterparts right now, but think of what things are going to look like in another 40, or even 20 years’ time, with virtual and augmented reality already trying to inch its way into our living rooms.

Musk explains:

"If you assume any rate of improvement at all, then the games will become indistinguishable from reality, even if that rate of advancement drops by a thousand from what it is now. Then you just say, okay, let's imagine it's 10,000 years in the future, which is nothing on the evolutionary scale. So given that we're clearly on a trajectory to have games that are indistinguishable from reality, and those games could be played on any set-top box or on a PC or whatever, and there would probably be billions of such computers or set-top boxes, it would seem to follow that the odds that we're in base reality is one in billions."

It might not be the most comforting thing in the world to think about - our reality isn’t at all what we think it is - but Musk says all of this being one big video game is about the best option we could hope for, given the alternatives.

"Arguably we should hope that that's true, because if civilisation stops advancing, that may be due to some calamitous event that erases civilisation," he said. "So maybe we should be hopeful this is a simulation, because otherwise we are going to create simulations indistinguishable from reality or civilisation ceases to exist. We're unlikely to go into some multimillion-year stasis."

As Ezra Klein reports for Vox, what Musk is referring to here is a famous thought experiment published by Swedish philosopher Nick Bostrom from the University of Oxford in the UK back in 2003.

Published in the journal Philosophical Quarterly, the paper, entitled "Are you living in a computer simulation?", argues that at least one of the following propositions has to be true:

The human species is very likely to go extinct before reaching a 'posthuman' stage; Any posthuman civilisation is extremely unlikely to run a significant number of simulations of their evolutionary history (or variations thereof); We are almost certainly living in a computer simulation.

So what exactly is this posthuman stage?

Bostrom talks about how, at the rate technology has been going, we can assume that at some point, a single computer could simulate the entire mental history of humankind - he calls this an ancestor-simulation - by using less than one-millionth of its processing power for 1 second.

If left to advance at the rate we have been so far, a posthuman civilisation could eventually get to the point where an "astronomical" number of these computers would be built. Within this massive network, we’d put replicas of the minds of our ancestors to play out their lives in a giant simulation.

Assuming these minds had a 'consciousness' - something that scientists are talking about right now, with the consideration that robots of the future might need human rights of their own - the argument gets pretty circular. It goes like this

"[I]t could be the case that the vast majority of minds like ours do not belong to the original race but rather to people simulated by the advanced descendants of an original race. It is then possible to argue that, if this were the case, we would be rational to think that we are likely among the simulated minds rather than among the original biological ones. Therefore, if we don’t think that we are currently living in a computer simulation, we are not entitled to believe that we will have descendants who will run lots of such simulations of their forebears."

Basically, what Bostrom is saying is that humans will either almost certainly die out before any of this even happens (hello, climate change); no advanced civilisations in the history of the Universe contained wealthy individuals who were interested in running ancestor-simulations; or we almost certainly live in a simulation.

In the talk below, Musk argues for the third option to be true, but Bostrom himself said that you can’t really choose between the three, based on the information we currently have about our own existence.

The problem with this thinking, Klein argues, it that it hinges on the idea that we’d be able to recreate consciousness in a video game, saying:

"I don't see a reason to believe that even very advanced civilisations will manage to easily simulate consciousness. But that's just what a simulated consciousness who believes he's a special participant in base reality would say, isn't it?"

Ugh, screw this, I’m going back to bed.

You can read the entire paper here, watch Musk’s argument below, and check out the wider debate at the simulation argument website. Just, if you fall down the rabbit hole and never get out, please don’t send someone to revenge-egg our houses, okay?