Professor Ericson: Very well, Mr. Cooper, how do you know you're not just dreaming butterflies can't dream?
Sheldon: Because I'm awake.
Professor Ericson: Or are you dreaming you're awake?
Sheldon: You can see I'm awake and you can hear me talking.
Professor Ericson: Yeah... I don't know. I saw some pretty trippy stuff at a Grateful Dead concert. The drummer turned into a tap-dancing walrus and floated away. So we can't really trust our senses, can we?
Sheldon: We can validate them by comparing them with other observers.
Professor Ericson: Mm, but that would mean we have to hear what they say, which requires... trusting our senses. Do you see a problem with your argument, Mr. Cooper?
Sheldon: I could concentrate better if you weren't flashing your toes at me.

Mary: Let's say grace.
Sheldon: Hang on, safety first. [puts mittens on]
George Jr.: When are you gonna get over that?
Sheldon: I would think recent events would make you value protection.
Mary: Enough.

Ms. MacElroy: Now, can anyone tell me why Melville shifts the narrative voice from Ishmael to Ahab? [Ms. MacElroy waits for somebody else to raise their hand] Sheldon.
Sheldon: I have a tummyache. I'd like to see the nurse.
Derek: A "tummyache"?
Sheldon: Yes, Derek, I have a tummy and it aches. Ergo, tummyache.
Derek: Ergo?
Sheldon: It's Latin, Derek.
Ms. MacElroy: Go to the nurse.
Sheldon: And to answer your question, the shifting point of view grants the reader a broader perspective of events than typically allowed by first-person narration.
Ms. MacElroy: Where were we?
Sheldon: And "ergo" is Latin for "hence," Derek.

Missy: What's it like to not believe in God?
Sheldon: It's great. Big fan.
Missy: Are you ever afraid you're wrong?
Sheldon: About religion? Never. About other things? Also never.

Professor Ericson: So we learned that the theory of knowledge poses some very serious problems.
Sheldon: [enters] Excuse me, Professor Ericson. I've done a little reading since last we spoke, and I'm prepared to show you that everything we know about science is true.
Professor Ericson: Well, I am all ears.
Sheldon: You said I couldn't truly know anything, but there is one thing that I do know. If I question, I must think; If I think, I must exist. Cogito, ergo sum: I think, therefore I am.
Professor Ericson: You're right.
Sheldon: You're darn right I'm right.
Professor Ericson: Guys, g-give it up for Sheldon. [applause] Now for a job well done... here is a flower full of sweet nectar.
Sheldon: Why would I want that?
Professor Ericson: Because you're a butterfly and this is just your dream.
Sheldon: I'm not a butterfly.
Professor Ericson: Are you sure? [laughs]
[Sheldon wakes up:]
Sheldon: It was a dream. Oh, no. [camera pans out] Help! I'm a butterfly! Nothing I know is real! Everything is a dream! Missy, help! [Missy holds a fly swatter] No!
[Sheldon wakes up:]
Sheldon: Missy, am I awake or is this a dream?
Missy: Shut up, dingus.
Sheldon: Okay, I'm awake.

Sheldon: I stopped at the library today and picked up books on epistemology, Descartes's dream argument and the foundations of scientific logic. Do you know what she's going to do?
Meemaw: Rue the day?
Sheldon: The day, the night. If it's rue-able, she's going to rue it.

Mary: Hey, Brenda.
Brenda Sparks: She didn't want you to walk her in?
Mary: No. How about Billy?
Brenda Sparks: Oh, I walked him in. Found his homeroom. Explained that "homeroom" is different than his room at home. Still not sure he gets it.
Mary: Tough day.
Brenda Sparks: Yeah.
Mary: You want to get some coffee?
Brenda Sparks: I was thinking vodka, but coffee will do.