"A duprass is a valuable instrument for gaining and developing, in the privacy of an interminable love affair, insights that are queer but true."
A duprass is a karass of only two people, which cannot be invaded by anyone or anything. This is part of Bokonon philosophy. They're rare. It could be Vonnegut saying, look here, yes, here's true love. Of the self-sufficient, self-absorbed kind. It happens occasionally, you may see it, but don't expect it. For the rest of us, let's thumb our noses at the gods, and love as well as we can.