The bottom line. An accounting term — the last line of the statement, where profit or loss appears — that became the general American word for the thing that finally matters. Everything above it is detail.
The proof of the pudding is in the eating. Not the recipe, not the cook’s reputation, not how it looks coming out of the oven.
If it ain’t broke, don’t fix it. Popularized by Bert Lance in the Carter administration. A working thing requires no examination of why it works.
Whatever works. Offered as a resolution rather than a shrug. It closes a debate about approach by declining to have one.
Don’t tell me, show me. An objection to the form of an answer rather than its content. Description is treated as insufficient in principle, whatever it describes.