Knowing the answer before you ask the question
The first rule of cross-examination at trial is that you never ask a question that you don’t already know the answer to.
Inquiry has a place. Inquiry in the pursuit of science, of discovery and of learning is essential. But inquiry almost never belongs in a presentation. That’s because the presentation exists to communicate what you already know, not to discover something new.
That’s why comedians try out their new material in small clubs.
That’s why you should try out your job interview answers long before you go on a job interview.
And that’s why you shouldn’t throw a steel ball at the window of the new truck you’re launching unless you’re really, really sure it’s not going to break.
[Either that, or know that what you’re selling is live magic, the possibility of ‘it might not work,’ the generosity of art in the moment. But they rarely belong in the same interaction.]