Chapter 2 of 9

Chapter 2: Epistemological Foundations

Assumption Mapping, Risk Architecture, and the mechanics of risk ranking.

Playbook Chapters
What You'll Learn By the end of this chapter, you'll know how to deconstruct your idea into testable assumptions, categorize risks using the D.V.F.+S framework, and identify the "Leap of Faith" assumptions that could kill your startup.

Your Idea Is a Bundle of Assumptions

Here's a mindset shift that changes everything: Your startup idea isn't a single thing. It's a bundle of interconnected assumptions—and most of them are probably wrong.

Before you can validate "your idea," you need to unbundle it into its component hypotheses. This process is called Assumption Mapping, and it's the foundation of rigorous validation.

Example: "An App for Dog Walkers"

That "idea" actually contains dozens of assumptions:

  • Dog owners want help finding walkers (desirability)
  • They'll pay for it vs. asking neighbors (viability)
  • We can build a matching algorithm (feasibility)
  • We can verify walker backgrounds cheaply (feasibility)
  • This market is growing (strategic)
  • We can acquire customers cheaper than they're worth (viability)

Each of these could be wrong. Some of them being wrong would kill the business.

The Four Categories of Risk (D.V.F.+S)

Every assumption in your bundle falls into one of four risk categories:

Desirability Risk

Do they actually want this?

  • Is the problem real?
  • Is it painful enough to solve?
  • Are they actively looking for solutions?

Primary risk for most startups. If nobody wants it, nothing else matters.

Viability Risk

Can we make money doing this?

  • Will they pay our price?
  • Is the market big enough?
  • Can we acquire customers profitably?

Secondary risk. You can have demand and still go broke.

Feasibility Risk

Can we actually build this?

  • Is the technology available?
  • Do we have the skills?
  • Can we build it at acceptable cost?

Usually lower risk for software. Primary risk for deep tech or hardware.

Strategic Risk

Should we do this?

  • Does this align with our mission?
  • Is the timing right?
  • Do we have the unfair advantage to win?

Often overlooked. Wrong timing or misalignment kills startups too.

The Tech Founder Trap

Technical founders often obsess over Feasibility ("Can we build it?") while ignoring Desirability ("Should we build it?"). The graveyard of startups is full of technically brilliant products that solved problems nobody had.

The Assumption Mapping Matrix

Once you've listed your assumptions, you need to prioritize which to test first. Use this 2x2 matrix:

Unknown (No Evidence) Known (Evidence Exists)
High Impact
If wrong, business fails		 TEST IMMEDIATELY
This is where startups die. All energy goes here.		 Verify & Monitor
Evidence exists, but keep watching.
Low Impact
If wrong, we adapt		 Test Later
Not urgent. Get to it eventually. 		Ignore
Low risk, evidence exists. Move on.

The Death Zone

The High Impact + Unknown quadrant is where startups die. If you're wrong about an assumption in this quadrant, your entire business collapses.

Your #1 priority in validation is moving assumptions out of this quadrant—either by getting evidence (moving them to "Known") or by discovering they're not actually that important (moving them to "Low Impact").

Identifying "Leap of Faith" Assumptions

Some assumptions are so fundamental that the entire business depends on them. These are called Leap of Faith assumptions—the beliefs that, if wrong, mean the whole venture collapses.

Uber's Leap of Faith

"People will get into a stranger's car."

This was a fundamental behavioral change. If wrong, no amount of good UX could save the business. They tested this before building elaborate matching algorithms.

Airbnb's Leap of Faith

"People will sleep in a stranger's home."

Another behavioral assumption. They validated this with ugly photos and spreadsheets before investing in professional photography or elaborate booking systems.

Exercise: Find Your Leap of Faith

For your startup, ask: "If this one thing is wrong, does everything else fall apart?"

Write it down. That's your Leap of Faith assumption. That's what you test first—before you build anything else.

The Simple Risk Ranking Test

You don't need complex frameworks to rank risks. Just ask one question for each assumption:

The Kill Question

"If this assumption is false, does the entire project collapse?"

If the answer is yes, it's a high-impact assumption. Put it in the "test immediately" quadrant.

What You Walk Away With

  • Unbundled Assumptions: Your "idea" broken down into testable hypotheses.
  • D.V.F.+S Classification: Each assumption categorized by risk type.
  • Prioritized Hit List: High-impact, unknown assumptions ranked for testing.
  • Leap of Faith Identified: The one assumption that matters most.

Now you know what to test. Next up: How to actually test it, starting with qualitative customer discovery.

Map Your Assumptions

Use our Assumption Mapping tool to identify D.V.F.+S risks and prioritize which assumptions to test first.

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Works Cited & Recommended Reading
Lean Startup & Innovation Accounting
Assumption Mapping & Testing
  • 7. Invest in Winning Ideas with Assumption Mapping. Miro
  • 10. Testing Business Ideas: Book Summary. Strategyzer
  • 11. Innovation Tools – The Assumption Mapper. Nico Eggert
  • 14. Business Testing: Is your Hypothesis Really Validated? Strategyzer
  • 16. An Introduction to Assumptions Mapping. Mural
  • 17. Assumption Mapping Techniques. Medium
Customer Interviews & The Mom Test
  • 8. Book Summary: The Mom Test by Rob Fitzpatrick. Medium
  • 22. The Mom Test for Better Customer Interviews. Looppanel
  • 23. The Mom Test by Rob Fitzpatrick [Actionable Summary]. Durmonski.com
  • 9. How to Evaluate Customer Validation in Early Stages. Golden Egg Check
Jobs-to-Be-Done Framework
  • 24. Jobs to be Done 101: Your Interviewing Style Primer. Dscout
  • 25. How To Get Results From Jobs-to-be-Done Interviews. Jobs-to-be-Done
  • 26. A Script to Kickstart JTBD Interviews. JTBD.info
Product-Market Fit & Surveys
  • 33. Sean Ellis Product Market Fit Survey Template. Zonka Feedback
  • 34. How to Use the Product/Market Fit Survey. Lean B2B
  • 35. Product Market-Fit Questions: Tips and Examples. Qualaroo
  • 36. Product/Market Fit Survey by Sean Ellis. PMF Survey
Pricing Validation Methods
Smoke Tests & Fake Door Testing
  • 43. Smoke Tests in Market Research - Complete Guide. Horizon
  • 45. Fake Door Testing - How it Works, Benefits & Risks. Chameleon.io
  • 52. High Hurdle Product Experiment. Learning Loop
  • 53. Fake Door Testing: Measuring User Interest. UXtweak
Conversion Benchmarks & Metrics
  • 46. Landing Page Statistics 2025: 97+ Stats. Marketing LTB
  • 47. Understanding Landing Page Conversion Rates 2025. Nudge
  • 49. What Is A Good Waitlist Conversion Rate? ScaleMath
  • 54. Average Ad Click Through Rates (CTRs). Smart Insights
Decision Making & Kill Criteria
  • 57. From Test Results to Business Decisions. M Accelerator
  • 58. Kill Criteria for Product Managers. Medium
  • 59. When to Kill Your Venture - Session Recap. Bundl

This playbook synthesizes research from Lean Startup methodology, Jobs-to-Be-Done theory, behavioral economics, and validation frameworks. Some book links may be affiliate links.