The thread's title is not what does the concept of fair mean.
It is, do the rich pay their fair share of taxes. When one asks, "what is fair?" in such a thread, a reasonable person would understand the question to mean, "what is fair?" (in the context of the conversation regarding tax progressivity)
So what exactly is fair? Given the amount the term has been used over the last several months, I would think there would be some consensus as to what it means.
Is fair when the rich forfeit all of their $ except enough to subsist on?
Is fair when they have to give up more than they take home?
What is fair? What is a fair way to address revenue issues, when the amount of money we need arithmetically can't be raised by the rich alone.
Is it fair to rain benefits on people who have no stake in paying for those benefits? Is it fair to burden future generations with the bill for an entitlement system that those receiving the benefits aren't willing to pay for?
Is it fair to ask our creditors to endlessly make up the difference?
Is it fair to ruin our financial stability in an effort to avoid any short term pain?
What is fair?