I spent a few minutes staring at the screen when SOMA ended. It's messed up, and even though you can see it coming, it's still heartbreaking and shocking. At the heart of SOMA's conclusion is something called the "coin flip" theory, which hardcore fans have been going back and forth on.
Warning: There are some major spoilers SOMA after this.
The first twist in SOMA is when players realise the main character, Simon, has been transported from sunny Toronto to an underwater facility overrun by nightmarish robots. But how? Simon's last memory is having his brain scanned, part of a recovery effort from a car crash that killed his friend and messed up his head. Simon's scan was transported to another body in PATHOS-II, where the game takes place. Simon is no longer Simon -- in a sense, he's now a clone.
For the purposes of this article, let's call him Simon 2.0. He has the memories of Simon 1.0 up until the brain scan, but lacks the remaining memories of Simon 1.0, who left the doctor's office and eventually died because of his brain injuries.
There are several moments in SOMA where the player reaches a crossroad and must transfer their consciousness from one body to the next. Think of this like copying and pasting a file on a computer. When the file is pasted, both versions still remain. The two have a common foundation, but can lead different lives.
Which file is the "real" file, or doesn't it matter?
This is at the heart of the "coin toss" that's mentioned by another PATHOS-II survivor, Catherine. When the consciousness transfer is triggered, there's a 50/50 chance you end up as the version of Simon who gets to keep going...or the one left behind. When either version wakes up, they don't know the answer to that question. There's no flashing box that says "Hey, you're Simon 3.0, congrats! You won the coin toss." Instead, the haunting truth slowly emerges.
When the transfer occurs, as Simon 2.0 is copied and births Simon 3.0, Simon 3.0 awakens and hears someone familiar talking around the corner: Simon 2.0.
Perhaps unsurprisingly, this causes Simon 2.0 to freak out.
Catherine: You know it's not magic. You were copied. The other Simon in the seat was copied...and now you are here. Just like Simon lived on in Toronto.
Simon 3.0: God damn you, Catherine. Two Simons? There can't be two Simsons.
Catherine: What did you think would happen?
Simon 3.0: That you were gonna take my mind and put it in another body, like a brain transplant.
Catherine: I'm sorry, it wouldn't work that way.
Simon 3.0: You realise how messed up this is?
As Simon 3.0, you have the option to kill Simon 2.0 or let him to live. There's no way for Simon 2.0 to survive -- PATHOS-II was rapidly crumbling -- so I decided to kill off Simon 2.0. Of course, it's easy to say that as the Simon that survived.
This moment -- and its implications -- continue to drive the game's conversation.
In SOMA, a comet hit Earth, destroying everything on the surface on the planet. The residents of PATHOS-II are the last remnants of humanity, but as PATHOS-II began to crumble, they looked towards another way of allowing the species to survive: the ARK. A hyper-realistic virtual reality, the ARK would be loaded onto a rocket, then take people's brain scans, dump them into the digital world, and launch everything into space. Earth was dead, but humanity, in a way, lives on.
But it's not possible to put you into the ARK. By "you," I mean version 1.0 of yourself. The scan is transferred into the ARK, which, by definition, is you 2.0.
This drove some people on PATHOS-II wild, unable to grapple with the concept of two versions of themselves existing at the same time. Suicides became rampant after brain scans, as people tried to resolve the psychological conflict.
The most recent expansion of the coin theory came from redditor nickdean16, who claims to be graduate student studying AI and Machine Learning:
nickdean16's interpretation is that it's not really a coin toss, it's a dice roll:
When you transferred from Simon 1.0 to Simon 2.0, Catherine explained what happened, but it's tough understand the gravity of everything; you get to continue as Simon 3.0.
In this sense, the player is always winning the coin toss. You don't die from brain injuries as Simon 1.0, nor rot away (or get shut down) as Simon 2.0. Instead, the player moves forward, becoming the latest version of Simon.
It's easy to assume this is always how it will always play out, and the game counts on this. In the ending, the player reaches the ARK and transfers their brain scan onto humanity's last ditch effort. But rather than waking up in a virtual world, you're still at a control panel.
You, Simon 3.0, are screwed. You lost the coin toss.
Simon 3.0: I'm still here...? I'm still here? Catherine? Catherine!
Catherine: I'm here.
Simon 3.0: What the hell happened? What went wrong?
Catherine: Nothing! They're out there, among the stars. We're here.
Simon 3.0: No, we were getting on the ARK. I saw it. It finished loading just before it launched.
Catherine: Yeah, I saw.
Simon 3.0: Then, why are we still here?
Catherine: Simon, I can't keep telling you how it works; you won't listen. You know why we're here. You were copied onto the ARK, you just didn't carry over. You lost the coin toss. We both did. Just like Simon at Omicron [another facility], just like the man who died in Toronto a hundred years ago.
As the facility goes dark, Simon 3.0 begins to realise his horrible predicament. Stuck at the bottom of the ocean, a copy of a copy of a copy, there's no hope. Yes, Simon 4.0 is out there in the stars, but Simon 3.0 will never leave Earth.
"Please don't leave me alone," he screams. "Catherine? Catherine?"
The coin toss shows no mercy.
There's a brief epilogue for Simon 4.0, however, in which he wakes up on the ARK with Catherine. Neither is aware of what happened to their previous selves.