Title text: Socrates could've saved himself a lot of trouble if he'd just brought a flashlight, tranquilizer gun, and a bunch of rescue harnesses.
The 911 operator references Plato's cave. This is a reference to an allegory by Plato in which he creates a world in which prisoners are chained against a wall and know only the shadows that cross the wall and how they create their own reality from those shadows. They would create words for the things they were seeing, but that would only correspond to the shadows and not the physical things themselves.
Cueball's brain seems to be unaware it is in his body, and is freaked out by the fact that all the information it receives is through Cueball's sensory organs. The brain has no means of verifying that the information received from the senses indeed corresponds to the actual outside world, and is thus in Plato's cave.
The title text continues with the Plato's cave and takes it literally; Randall is saying that Socrates, Plato's teacher, should have just gone into the cave and brought the prisoners out instead of dealing with the extended allegory. The tranquilizer gun is for the prisoners, so they don't completely freak out while being taken out of the cave.
- [Cueball is on the phone.]
- Cueball: Hello? 911? I'm trapped!
- Cueball: It's dark and I can't see anything except these two distorted splotches of light!
- Cueball: Help!
- [The 911 operator is in an office, wearing a headset.]
- Ponytail: Splotches of light? Your... eyeballs?
- Cueball (over phone): I think that's what they are! There's meat everywhere!
- Ponytail: ...so you're a brain.
- Cueball (over phone): Yes!
- Ponytail: Yeah, we all are. You're not trapped. Use your body to walk around and experience reality.
- Cueball: But everything's just signals in my sensory cortices! How can I be sure they correspond to an external world?!
- Ponytail (over phone): I'm sorry, but we can't send a search-and-rescue team into Plato's cave.