Every mental model you carry was built during a period when certain things were true — and quietly keeps running long after those conditions have changed. The medieval logician William of Ockham noticed something subtler than his famous razor: he argued that the mind's 'habit of assent' — the tendency to keep affirming what once proved useful — is itself a kind of cognitive inertia, distinct from the original evidence that created it. Modern cognitive scientists call a version of this 'entrenchment,' but Ockham's framing is more useful for product leaders because it locates the problem precisely: it's not that you're ignoring new data, it's that the model stopped being a live hypothesis and became an unexamined fixture. The practical move isn't to audit all your models at once — that's paralyzing. It's to pick the one that governs the most decisions right now and ask yourself honestly when you last encountered evidence that actually updated it. If you can't remember, the model has probably become furniture.

What is the opposite of what you're currently doing to test your most load-bearing mental model — the one that quietly shapes the most calls you make?

Drawing from Scholastic Philosophy / Medieval Logic — William of Ockham (Ordinatio / Quodlibetal Questions, c. 1317–1324)