"Educated Idiot" joke

During the tea break, John and William were chatting:
John: William, I've been taking night courses for 5 months now and I have an exam next week.
William: oh!
John: For example, do you know who is Graham Bell?
William: No
John: 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:
John: Do you know who is Alexander Dumas?
William: No
John: He's the author of' The 3 Musketeers', if you take night courses, you would know this.
The next day, once again:
John: And do you know who is Jean Jacques Rousseau?
William: No
John: He's the author of' Confessions', if you take night courses, you would know this.
This time, William got irritated and said:' And you, do you know who is George Hunt?'
John: No
William: He's the guy enjoying with your wife while you are doing night courses!! If you stop night courses, you would know this...