Is your life really your life, or is it actually the dream of a butterfly? Or is it a complex computer simulation indistinguishable from "real" reality? Don't worry, it's just a glitch in the Matrix. It happens when they change something.
Questions about the nature of reality weren't invented by high-as-a-kite college sophomores. Chinese philosopher Zhuangzi noticed sometime around 300 BCE that his dreams of being something other than human (a butterfly, most famously) were indistinguishable from his experience being Zhuangzi. He could not say with certainty that he was Zhuangzi dreaming of being a butterfly rather than a butterfly dreaming of being Zhuangzi.
The whole "reality is an illusion" idea has been kicked around by everyone from Siddhartha to the existentialists. It is Oxford philosopher Nick Bostrom who is most often associated with the idea that we are living in a computer simulation. His premise is based on a series of assumptions:
1). A technological society could eventually achieve the capability of creating a computer simulation that is indistinguishable from reality to the inhabitants of the simulation.
2). Such a society would not do this once or twice. They would create many such simulations.
3). Left to run long enough the societies within the simulations would eventually be able to create their own simulations, also indistinguishable from reality to the sub-simulations inhabitants.
As a result, you have billions of simulations, with a nearly infinite number of cascading sub-simulations, all of them perfectly real to their inhabitants. Yet there is only a single ultimate progenitor society. The math is actually pretty simple: the odds are nearly infinity to one that we are all living in a computer simulation.
One very strong argument against this unsettling theory is that a computer with the computational power to accomplish this is impossible. Setting aside the fact that today's computational power surely seemed unimaginable 100 years ago, there's a more interesting solution – the computer only actively simulates what it needs to. This is something that actually happens in modern computer games, and you've seen it if you've ever moved faster than your graphics card was capable of rendering the scenery, as the trees and buildings that had previously been beyond your view were drawn on the screen before your eyes. It actually explains a few of the trickier things about quantum physics, like why particles have an indeterminate position until they're observed.
Even more disturbing, it may be a much smaller simulation that you think. There could be just a few active simulation inhabitants, with the rest of the world filled with "non-actor" or NPC characters controlled by the computer. Their actions are only simulated as you perceive them, carefully performed so as to present the illusion that they have entire lives separate from yours. This helps explain why the creepy homeless guy at the end of your street doesn't seem to do much other than hang out and ask you to bring him 10 dire wolf pelts.
If all that seems too weird, let's just kick it back to Zhuangzi. There are almost seven billion people in the world. They all sleep. They all dream. Odds are we're all just living someone else's extremely vivid dream.
Source: Bostrom, Nick. "Are you living in a computer simulation?" Oxford University.
Butterfly photo: Lindsay Sorensen.