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As of 2025, Highline Beta argues that the Assumption Matrix—a tool that scores assumptions on criticality and uncertainty—prevents teams from testing what's easiest rather than what's riskiest, helping ventures avoid fast progress in the wrong direction.
New ventures typically generate 20-30 assumptions across desirability, feasibility, and viability, but most teams prioritize testing what's easiest rather than what poses the greatest risk. Highline Beta's Assumption Matrix addresses this by scoring each assumption on two axes: criticality (whether the venture fails if the assumption is wrong) and uncertainty (how much real evidence exists). Teams should focus first on assumptions that are both critical and uncertain, then design minimal experiments like fake landing pages or clickable prototypes to test these high-risk areas before moving to less critical assumptions.
The matrix forces teams to distinguish between what's easy to test and what's actually risky to get wrong. By scoring assumptions on criticality and uncertainty rather than convenience, teams avoid the common trap of making fast progress in areas that don't determine venture success. Highline Beta emphasizes that if a proposed feature doesn't tie back to a critical, uncertain assumption, it should wait until core risks are validated.
Assumptions should be mapped across desirability (will users care about the problem and choose this over existing solutions), feasibility (can it be built within technical, governance, legal, and regulatory constraints), and viability (will people pay and can the segment be served sustainably). The goal is to generate 20-30 assumptions total, going beyond obvious ones to surface assumptions that haven't been verbalized yet.
The most effective experiments are small and scrappy, designed at varying fidelity levels depending on the venture stage. Examples include fake landing pages, clickable prototypes, sacrificial concept descriptions, and pricing tests or smoke screens. Each experiment should tie back to specific questions from the matrix, and teams can test multiple assumptions within a single experiment to maximize efficiency.
When venture plans get stuck in circular debates, the issue is typically that critical assumptions haven't been prioritized or even identified. The matrix creates shared language around learning priorities and aligns internal stakeholders around the logic of what's being tested and why. This structured approach transforms endless discussions into focused experimentation plans that unlock forward movement.
If you missed last week's edition, you can find it here.
Every new venture starts with a stack of assumptions. Some are obvious, some are hidden.
The challenge isn’t listing them out. It’s knowing which ones to test first.
The Assumption Matrix is a simple tool to turn a long list of assumptions into a focused test plan.
It helps avoid wasted effort, focus on real risk, and move faster with more confidence.
Here’s how it works.
Start by mapping assumptions across three categories:
Try to write 20–30 assumptions. Volume matters. The goal is to go beyond the most obvious, and surface what hasn’t been verbalized yet.
Not all assumptions are equal. The matrix helps you score each one on two axes:
Place each assumption on a 2x2 grid:
First, focus on assumptions that are both critical and uncertain, because that’s where the risk lives.
Too many teams jump to what’s easiest to test, not what’s riskiest to figure out. That’s how you make fast progress in the wrong direction.
The Assumption Matrix helps you:
It’s also a powerful tool for saying no to distractions. If a proposed feature doesn’t tie back to a critical, uncertain assumption, it can wait. Once the core underlying assumptions of a venture have been validated, you can move on to the less critical and more certain ones.
Once you’ve mapped the top assumptions, design the smallest, scrappiest experiments to test them. These sit at varying levels of fidelity, depending on where you are in the journey and the desired approach. Examples include:
Each one is tied back to a specific question from the matrix, keeping in mind you can test multiple assumptions in one experiment
Don’t test for the sake of testing. Test to unlock movement.
If your venture plan feels stuck in circular debate, the problem isn’t the idea, it’s the assumptions no one has prioritized or even named yet.
The Assumption Matrix is how we fix that. Every time.
