An Estimate for the Impossible

The word “impossible” often hides a more precise constraint.

The psychologists Roger Buehler, Dale Griffin and Michael Ross asked people to estimate how long their own tasks would take — including finishing their theses. Even when participants were asked for a realistic forecast, they mostly built it on the ideal scenario: how the work would go if nothing significant got in the way. Their own past experience of delays was used remarkably little.

That is how the “planning fallacy” got its experimental description. It does not mean that every deadline should automatically be multiplied by two. It is more useful to add an outside view: how long similar tasks took before, which stages depend on other people, and where in the schedule there is room for ordinary life, which for some unknown reason keeps happening.

Impossible right now. Impossible on the available budget. Impossible alone. Impossible without breaking the law. Impossible while keeping every other condition unchanged.

Once it is made precise, there is work to do.

You can change the deadline, the scope, the technology, the people involved, the location, the criterion of success and the order of the stages.

Not every impossibility disappears after good planning. Physical laws, health, other people’s freedom and limited resources exist independently of optimism.

But an estimate is useful precisely because it separates a real limit from a bundle of incompatible wishes.

Sometimes a project is impossible only because it has to be fast, cheap, perfect and free of changes. Drop one adjective and it suddenly acquires a calendar.

“Impossible by Friday” translates into an estimate in several different ways. Impossible while three people are doing it in the time left over from their real jobs. Impossible if every step goes through approval in two departments. Impossible in full, but possible by half, if the client agrees to call the second half version two. Until someone writes those lines out, the argument is not about the project but about the strength of character of the people in the room.

The convenient thing about the word “impossible” is that it does not require naming a price. An estimate does: it forces someone to say out loud that he is giving up the deadline, the scope or the money. That is usually why people dislike drawing one up.