In 1969, when we again demonstrated at Madison Square Garden, Duncan-sensei amazed the audience by disarming an attacker -- portrayed by one of us -- who was whipping and twirling a nunchaku against him at full speed. Not having advanced knowledge of Sensei's plans, even we were stupefied by his incredible degree of skill at not being struck while taking the thrashing weapon from a trained dojo-mate.
Afterwards, back at the dojo, the other students and I were equally amazed and conflicted by the demonstration we ourselves had been part of at the Garden. The lead black belt expressed to Sensei the confusion we were all feeling.
"Sensei, we had begun to believe that the lethal weapons we train in were the epitome of our skill at personal protection and dominance over our opponents. We work relentlessly to keep those weapon skills honed and polished, as we would a lethal katana. Yet today you seemed to negate our armed skills while being completely unarmed. Is our weapons training then a waste of time?"
"Never become complacent," Sensei somberly told us that day. "Your audience during a demonstration is like your enemy: surprise them and you can likewise surprise an actual opponent. But become complacent and predictable, and even your opponent will know the depth of your skill."
He paused to let us process that, then continued. "Right now you are all capable of surprising a bigger and stronger opponent when, as he makes a move on you, you reveal and use a concealed ninjutsu weapon against him. He doesn't expect it, and perhaps doesn't even know what it is. That momentary confusion is your advantage."
"Today I probably surprised the lot of you because you, too, did not know my intention, nor the depth of my small skills -- much like the audience -- or like an enemy. You're conflicted because you believe up till now that weapons were superior to unarmed hands and feet. I demonstrated otherwise."
"So Sensei, which is it," I cautiously asked. "Weapons or empty hands?" I was very impatient at 16.
"It's knowing both," said a dojo-mate who thought he was smart.
"No, it's using whatever you have at the time-- weapon or empty hands, " said another dojo-mate who thought he was smarter."
"No," said Sensei. "It's knowing that there is always another approach to what you think you already know. It's never becoming overconfident or complacent. It's knowing that every coin has two sides!"
That was my first exposure to the philosophical tenet we call: "The Other Side of the Coin."