Such was the case a few weeks ago. I was upstairs working at the computer; William was downstairs barking. We had just come in from a long walk, so I knew he didn't have to go. He had licked the cat bowl clean hours before, so it couldn't be that. I had given him fresh water when we came home from the walk, so it wasn't that either. Since I was quite convinced that William really didn't need anything, I tried to ignore the barking, but finally, driven to distraction, I went downstairs to find out what the problem was. William, I discovered, was barking at the couch.
The couch, which is really a kind of daybed, has two rows of pillows at the back. The first row of pillows had all flopped down, covering the seat and preventing William from lying there. I propped the pillows back up where they belonged, William jumped up on the couch and lay down, and peace and quiet were restored.