There has to be a mechanism for people who are truly passionate about their work, like artists, scientists, programmers, to follow their passions as far as they want. The danger, of course, is that intra-organization competition pressures people to work longer and longer hours. I'm willing to accept that risk so long as we make a shorter work week the default.

We're talking about an unusual case, though. You have to realize the most people hate their jobs. They're not following their passions. They find work tedious, uncomfortable, and frequently demeaning. For these people, the bulk of humanity, a cap on working hours frees them to do something they find much more interesting.