Dealing with workers who don't

I firmly believe that people want to do a good job at work. Humans are industrious by nature (contrary to popular belief that we're naturally lazy and will be slugs forever if given the chance), and we seem to really want to be seen as competent and capable. It isn't often we're presented with workers who just, well, don't.

Workers who don't work are kind of a puzzle. Someone whose work is below par has a product that can be judged as lacking, goals for improvement can be set, and progress can be charted. But there has to be work done for any of that to be possible. What does one do when there is nothing to judge? Not poor performance, but a complete and utter lack of performance?