Sheldon: Normally I don't like facial hair, but Spock makes it work.

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.

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.

Mary: Sheldon, faith means believing in something you can't know for sure is real. And right now, I am struggling with that.
Sheldon: So you don't believe in God anymore?
Mary: That isn't something for you to worry about. I need to figure this out myself.
Sheldon: Can I help? Maybe I could provide a fresh perspective.
Mary: I don't think so, baby.
Sheldon: Did you know that if gravity were slightly more powerful, the universe would collapse into a ball?
Mary: I did not.
Sheldon: Also, if gravity were slightly less powerful, the universe would fly apart and there would be no stars or planets.
Mary: Where you going with this, Sheldon?
Sheldon: It's just that gravity is precisely as strong as it needs to be. And if the ratio of the electromagnetic force to the strong force wasn't one percent, life wouldn't exist. What are the odds that would happen all by itself?
Mary: Why are you trying to convince me to believe in God? You don't believe in God.
Sheldon: I don't, but the precision of the universe at least makes it logical to conclude there's a creator.
Mary: Baby, I appreciate what you're trying to do, but logic is here. And my problem is here.
Sheldon: Well, there are 5 billion people on this planet and you're the perfect mom for me. What are the odds of that?

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.