Introduction
When you work on a long-term project, you may have experienced situations like:
- Something unexpected happens and the project drifts far away from the original plan
- You start a task and suddenly encounter unforeseen issues, which create even more tasks
These are what we call “Unknown Unknowns.”
The term dates back to a 2002 press briefing by U.S. Secretary of Defense Donald Rumsfeld. In response to questions about whether Iraq possessed weapons of mass destruction, he explained that information falls into three categories:
- Known Knowns: things we know
- Known Unknowns: things we know we don’t know
- Unknown Unknowns: things we don't even realize we don't know
He emphasized that the last category is the most troublesome—risks that come from outside our predictions can easily distort entire strategies.
The same phenomenon appears in everyday life and work. Hidden gaps in requirements and tasks that only reveal themselves once you start working are classic examples of Unknown Unknowns.
Why are Unknown Unknowns so difficult?
You may already have an intuitive sense by now. But let’s break down the main reasons Unknown Unknowns are so disruptive:
- They’re not included in the original plan, causing extra workload, cost overruns, and schedule delays
- When they appear, your entire prioritization shifts
- They create branching tasks that snowball into even more work
They also tend to show certain patterns:
- Strict top-down plans are especially vulnerable
- Creative fields, development, and research environments encounter them frequently
How to deal with them
The core problem is simple: you can’t prepare for what you don’t know.
And depending on what you’re working on, the best approach will differ. Still, the following strategies are widely effective:
1. Build buffer time into your plan
Since Unknown Unknowns will always occur, it’s more realistic to schedule from the start with the assumption that things won’t go perfectly.
- Set deadlines earlier than necessary
- Reserve buffer days
- Estimate workload with an extra 20% margin
This “padding” helps absorb surprises that arise later.
2. Start small and start early
Especially in development or creative work, there’s terrain you can only see once you start moving.
- Build a prototype
- Run a test version
- Gather early feedback from users or team members
By creating a mini version early, you surface Unknown Unknowns long before they become critical.
3. Use plans that can evolve
The more rigid the plan, the more fragile it becomes.
- Allow yourself to revise the plan
- Adjust priorities as needed
- Permit specification changes
Projects that assume flexibility from the beginning can adapt when the unexpected happens.
This is the idea behind evolutionary planning.
Conclusion
I personally tend to prefer top-down planning—laying out a long-term roadmap, listing all foreseeable tasks, and arranging them in a structured tree. But looking back, almost none of my long-term plans have gone exactly as expected. The biggest reason is Unknown Unknowns. Problems or tasks that were invisible during the planning stage always show up once I start moving.
But these deviations shouldn’t be seen as failures. They’re part of the premise.
What matters more than a perfect plan is a flexible plan—one you can update as reality unfolds.
That’s why the real strength behind long-term projects is not rigid scheduling, but the willingness and ability to continuously adjust course.
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