Ch. 9: Identifying Hidden Assumptions

This reading-guide post kicks off a monthly book club around Teresa Torres's Continuous Discovery Habits, focusing on Chapter 9, which covers identifying hidden assumptions. The chapter argues that teams should test the individual assumptions underlying an idea rather than whole ideas, and it introduces five assumption types: desirability, viability, feasibility, usability, and ethical. It points to story mapping, pre-mortems, and assumption mapping as practical ways to surface these beliefs and find the riskiest 'leap of faith' assumptions. The post is mainly a participation framework: reading schedule, discussion prompts, team exercises, and supplementary resources. Its core practical value lies in the exercises and the emphasis on questioning beliefs before investing in building.

01Key takeaways

• Test the individual assumptions behind an idea, not the whole idea, to learn faster and waste less effort.
• Check every idea against five assumption types: desirability, viability, feasibility, usability, and ethical.
• Story map the solution from the user's perspective, then question each step for hidden assumptions.
• Run a pre-mortem at the start to imagine failure and surface risky beliefs before investing time.
• Plot assumptions by importance and evidence strength, then test the important, weakly supported ones first.

02Key sections

Why test assumptions, not whole ideas

The chapter's central premise is that teams should break product ideas into the underlying beliefs that must hold true. Testing those beliefs is more efficient than validating an entire concept at once.

The five assumption types

Every product idea rests on desirability, viability, feasibility, usability, and ethical assumptions. Naming these categories helps teams notice which kinds of risk they have been overlooking.

Story mapping and pre-mortems

Story mapping lays out the steps end-users take to get value, which exposes hidden assumptions at each step. Pre-mortems ask what could go wrong before work begins, surfacing risks early.

Assumption mapping and leap-of-faith assumptions

Placing assumptions on a grid of evidence strength versus importance highlights the riskiest ones. The top-right corner, important but weakly evidenced, is where testing should start.

Discussion, exercises, and resources

The post pairs individual and team reflection prompts with timed exercises, plus supplementary reading and live session details. These are designed to turn the chapter's ideas into a regular habit.

03From the post

“Continuous Discovery Habits turns five this year. And to celebrate we are reading the book together. Each month, I am releasing an in-depth reading guide that includes: - The chapters we will be reading - A preview of the most important concepts we'll be learning about - Short videos you”

04Frameworks mentioned

Summary and takeaways written by PM Atlas; quotes are short excerpts. © the original author.