He says not to start with a joke, but he delivers this line as a joke (and the class laughs). So now I don't know whether to start with a joke or not!
Phenomenal talk.
The joke is almost 5 minutes into the talk: he didn't start with one. His point is that in the first few minutes the audience is still warming up and many wouldn't pay attention to the joke.
The joke is almost 5 minutes into the talk: he didn't start with one. His point is that in the first few minutes the audience is still warming up and many wouldn't pay attention to the joke.