Scott Bellware's framing: software is the only discipline where you can ignore the laws of physics and the machine still runs — but the team pays in lost velocity over time. Treating coupling, cohesion, and transparency as universal structural laws (not software-specific) lets teams start at a pace and maintain it forever. TDD matters because tests-first software is transparent — testability is a fundamental engineering property — and the setup code in tests is the real quality signal: the more setup you need, the lower-quality the system.