Comment by michtzik

> I explained that anything less than a progressive tax was going to make the poor pay more and the wealthy pay less.

Here's a formally-verified proof in Lean that with a flat tax, if you have more income, then you pay more tax: https://live.lean-lang.org/#codez=JYWwDg9gTgLgBAWQIYwBYBtgCM...

The theorem uses one important assumption: that the flat tax rate is positive.