Quite a few years ago Katie and I were retrieving our daughter, Liza, from an after-school visit to a friend’s house. As we were talking with the kid’s mom, a UPS truck arrived in the driveway and the resident dogs, two full-grown German Shepherds, noisily announced the new guest, barking and jumping and barking and jumping.
The delivery man was leery about getting out of his truck with two apparently ferocious dogs jumping and barking just a few feet away. He looked to the owner to restrain her pets.
“Oh, don’t worry,” she said. “They won’t bother you. We have an invisible fence.”
The UPS man looked at the woman; then looked at the dogs, studying the edge of the yard where the dogs were jumping and barking. He looked back at the woman and asked, “Can the dogs see it?”