"I mean..." Ned begins but catches himself. There's something in Charlie's tone that gives him pause. Something that's less like incredulity and more like genuine confusion.

After how upset Charlie had just been saying he is about feeling like he's in the dark about so much, about knowledge he doesn't have access to just because of when he's from, Ned wants to be cautious. So before he answers one way or another he asks.

"Is that... disbelief, or are you really asking me what a robot is?"