There is a reason why The Matrix was surprisingly popular when it burst onto the scene in 1999, making over 27 million opening weekend and winning 4 Oscars. Ok, a lot of that had to do with the new special effects, the Kung Fu fighting, and the leather. But another reason that the Matrix is my favorite movie of all time is how it discussed, portrayed, and played on the age-old question--What is Real?
Plato imagined that everything that we call 'real' might be a reflection, or shadow, of another real (really real) world. His analogy was that we were tied up in a cave, with a fire lighting the cave wall, and the only thing we ever experienced were shadows of the real world on the cave walls.
The Cave, of course, is an analogy for our sense organs. Rene Descartes picks up on this theme during the explosion of Newtonian science, saying that if our senses sometimes deceive us (illusions, hallucinations, dreams)--then perhaps they always deceive us? Descartes imagines that we are all being controlled by some sort of evil intelligent being capible of deluding our senses consistently.
Enter The Matrix:
MORPHEUS: "If real is what you can feel, taste, smell, and see, then 'real' is simply electrical impulses interpreted by your brain."
The Matrix imagines that powerful futuristic machines, given enough knowledge of how the human brain works, have subjected us to a new form of slavery, a "prison for your mind," a virtual world that humans are plugged into.
Of course, all of this is silly, and just philosophical thought experiments used to shed light on our limitations. But what I find amazing is that these silly thought experiments are, if you think about it, possible; and we could never really know either way.