"Joe, I have to say it. I'm going to swear Mom and Dad to secrecy, and none of us will ever breathe a word of this or anything that will lead to this conclusion to anyone else, ever, for all eternity. Mom, Dad, I need you to swear this oath by… all of our lives: that you will never repeat anything Joe has just said about his nature, or what we're about to discuss. Not ever, not to anyone. Swear it."
"I swear never to tell," Mom said instantly.
"Tim, if we had computers like this, even fractionally as powerful…" Dad began.
"Dad, you still don't understand what Joe just said… I need your oath. I suspect your silence on the subject could be forced, but I hope that's not necessary."
He looked at me intently, trying to decipher what I was saying, what Joe had said that could be so sensitive. Finally, he just capitulated, "I give my oath to keep the secret."
