He'd fill the blackboard with mathematical hieroglyphics that would give Einstein headaches, say "It is intuitively obvious that [something or other]", turn back to the blackboard and perform some seemingly magical manipulation whereupon the entire mess would collapse on itself with the answer being something like three and a half. Needless to say this left the rest of us looking at each other like something had just zoned-in from The Outer Limits, thinking "What the !!! was that?!"
Sherlock Holmes, in one of his stories, (I forget which one), made a very pithy comment when he said "There is nothing more deceptive than an "obvious" fact"
This is a statement that should be permanently tattooed onto the palm of every QA individual in the world.
If I were to write a "Ten Commandments" for QA, part of it would be those words that should strike fear in the heart QA engineers and testers all over the world:
Why are these words a problem? Because these words are the flashing red strobe lights that warn us about assumptions involved in design, requirements, or test, and we need to remember that these assumptions may not be true all of the time. In fact, they may signal a special case that is "assumed" to be true all of the time, or that something seemingly obvious to us is obvious to everyone else.
And THAT lies at the heart of QA's biggest failures. It's like a politician looking you straight in the eye and saying "Trust me!"
In it's purest essence, whenever you hear a broad blanket statement about something or other, it signals a potential weakness that should be given extra scrutiny during test or verification. In other words, we should be continually vigilant toward the "obvious", be it in requirements, design, or verification of what we do.
What say ye?