Many founders underestimate the number of assumptions behind their business models. While they can articulate their vision and highlight their unique solutions, they often struggle to identify the underlying theses that must hold true for success. The common practice of using Total Addressable Market (TAM) analyses tends to obscure these assumptions, leading to a lack of clarity about the real risks involved. Founders and investors may rely on the familiar TAM formula—potential customers multiplied by potential price—but this approach often fails to inform better decision-making and allows for a lack of transparency regarding growth assumptions. A more effective method involves assessing what the market currently spends on the problem being solved. This approach grounds founders in reality and forces them to clearly state the assumptions necessary for market growth. By starting with existing spending, founders can articulate the specific changes required for significant market expansion. Each of these changes represents a thesis, and founders often stack multiple theses without realizing the compounded risk. Understanding this risk can significantly impact how founders allocate their time and resources. The article emphasizes the value of recognizing actual risks rather than just presenting a polished TAM slide. By listing their theses, founders can identify how many factors need to align for success and distinguish between speculative and structural risks. Historically, venture capitalists would help founders navigate this process during due diligence, but the rush to invest has led to a neglect of this important analysis. Founders must either seek investors willing to engage in this deeper exploration or take on the responsibility themselves. The most successful founders are those who know precisely which assumptions they are working with and how speculative each one is, which ultimately separates a well-reasoned business strategy from mere storytelling in pitch decks.