He looked at me befuddled, "Um, so does that mean paper, or plastic?"
After making a long pompous statement like that, I couldn't just back down, so I insisted that he stitch together two bags, one plastic, and one paper, to make something that was a little of each. When you firmly proclaim something wrong, it's embarassing to back down.
It turns out that when you use a paper/plastic hybrid bag, your groceries all turn into an equal mass of bees. Let this be a lesson to all of you.