D: You can compute that by finite differencing.
M: But you've done a projection!
D: Yes, but the operations commute.
M: You're wrong, and I'll tell you why.
D: Sounds good. You tell me why I'm wrong, and then I'll say why you're wrong.
M: Great! ...
I eventually convinced him that I was right. Now I can go home and eat.
- Currently hearing: A loud discussion about the volume of spam received at different accounts