I don't think his definition is completely satisfying, but I love this discussion since developers so often use the term "business logic." It's one of those terms that we can't immediately define, but we <i>just sorta know</i> what it means. If it looks like business logic, talks like business logic, you know the drill.<p>I've noticed a similar idea when trying to classify issues in an issue tracker for a software project. We realized that using tags called "cosmetic" and "feature request," it sometimes gets hard to distinguish between the two, especially in GUI (or web) applications.