Main idea

The moment you ask yourself "how will I know it's finished?" decides the answer. Asked at the end of a project, the question arrives when you already have a list of accomplishments in front of you; the criterion retained will be one of them, because it is the only one that demands no further work.

Asked before you begin, the same question has no convenient way out: nothing is done yet, so no criterion is already satisfied. You are forced to describe the object of the work rather than the work — to draw up the list of what will have to be covered, and a way of counting it.

Hence the countermeasure, which bears not on the quality of the criterion but on when it is chosen: choose the stopping criterion at the start, not at the end. It is the difference between "I've tidied everything that was lying on my desk" and "here's the list of what I had to tidy, and it's all ticked off". The first sentence is true and commits to nothing; the second requires having made the list before starting.

Why it matters

It is a procedural countermeasure, so it applies without requiring any particular clear-sightedness at the critical moment — precisely when end-of-project tiredness makes any proof of completion attractive.

It also serves as a framing clause for delegated work: the criterion is part of the instruction, on the same footing as the scope, and not part of the report.

Nuances and limits

The criterion chosen at the start may turn out to be wrong along the way — the object reveals itself as you describe it. It must therefore be revisable, but explicitly and with its reason, which is still different from picking a new one because the old one resists.

And it doesn't exempt you from making it measurable: a criterion set at the start but unverifiable is worth no more than a convenient one set at the end.

Open questions

• How do you formulate a stopping criterion at the start of exploratory work, when the list of what has to be covered is only knowable as you advance?