A classic problem is knowing how many unknown unknowns you'll run into.

The best bet is to use a boring solution that has been used in a large number of similar situations successfully.

The successful uses in the past wrung out the unknown unknowns.

But sometimes you have no choice but to try a solution that has some degree of novelty.

Perhaps for example it's been used successfully in other contexts, but never in this organization.

The success or failure of novelty comes down to the rate of unknown unknowns.

How do you estimate the rate of unknown unknowns?

There's no good way–that's the fundamental problem.

The best way is to look at how many unknown-unknowns you've tripped over working on this project so far.

The unknown unknowns will all feel like random little niggling annoyances that required side quests.

They will feel like happenstances, but that's the entire point–they were unforeseeable.

Look at the rate of how many of those have shown up so far on the journey.

Is it higher or lower than you would have expected?

How far into the journey to getting a viable solution does it feel like you? 20%? 80%?

If you're sensing clear hints of viability, implying that you're almost to the other side of the jungle, that's a great sign that there's only a small amount of remaining territory for unknown unknowns to lurk in.