What is knowledge?

During work, Robert and Dilbert were chatting:

Robert: Dil, I've been attending night classes for 5 months now and I have an exam next week.
Dilbert: oh!

Robert: For example, do you know who is Graham Bell?
Dilbert: No
Robert: He's the inventor of the phone in 1876; if you take night Courses you would know this.

The next day, the same discussion took place:

Robert: Do you know who Alexander Dumas is?
Dilbert: No
Robert: He's the author of "The 3 Musketeers", if you take night courses, you would know this.

The next day, once again:

Robert: And do you know who 'Jean Jacques Rousseau' is?
Dilbert: No
Robert: He's the author of "Confessions", if you take night courses, you would know this.

This time, Dilbert got irritated and said: And you, do you know who is Robin?
Robert: No
Dilbert: He's the guy roaming with your wife!! If you stop night courses, you would know.