What is definitions in thinking?

Definitions in thinking is a concept in personal epistemology: The definitions you use quietly shape every conclusion built on top of them.

Example: Two engineers argue for an hour about whether their system has 'high availability.' One means 99.9% uptime measured monthly. The other means zero user-visible errors. They aren't disagreeing about architecture — they're running two different conversations with the same words. The moment someone asks 'what exactly do we mean by high availability here?' the dispute doesn't get resolved. It dissolves. It was never a real disagreement. It was a definition collision.

This concept is part of Phase 2 (Atomicity and Decomposition) in the How to Think curriculum, which builds the epistemic infrastructure for atomicity and decomposition.