The most dangerous moment in building a product isn't when you don't know something — it's when you've stopped noticing that you've stopped questioning. The 19th-century American philosopher Charles Sanders Peirce called this 'the fixation of belief': the way the mind, once it finds a working answer, naturally hardens that answer into an unexamined assumption and defends it against new evidence not because the evidence is wrong, but because re-opening the question feels destabilizing. Product teams do this constantly. A positioning decision made under last year's constraints becomes 'just how we think about the market.' A user segment chosen for pragmatic reasons becomes 'our customer.' The map calcifies into the territory. Peirce's remedy was what he called the 'scientific method of belief-fixation' — not science as a body of knowledge, but as a disposition: staying genuinely open to the possibility that your current model is the thing that needs revising, not the incoming data. Practically, this means treating your most confident product assumptions as the ones most worth stress-testing — specifically because confidence is the feeling that accompanies fixation, not just correctness.

Which product conviction do you actively avoid putting in front of users or data — and what would it cost you to be wrong about it?

Drawing from American Pragmatism (Peircean branch) — Charles Sanders Peirce (The Fixation of Belief, 1877)