The context of the following conversation is While others were fairly sure of their decision, Aubrey's idea caused a shadow of doubt in their mind.:
Aubrey says I know I'm right and I know that everyone else is mistaken, but I think that everybody else believes I'm wrong..
The friend responds About what?  What are you sure you're right about?.
Aubrey responds The Earth is flat.  The entire idea of a "round" Earth is just stupid.  Don't you think?.
The friend responds Ummm....well...I have heard of the idea of a flat Earth before..
Aubrey responds You didn't answer my question, Derrick.  You don't believe that the Earth is round, DO YOU???.
The friend responds Everyone has their own believes!.