Yes. It is nebulous. But one cannot say that it is so nebulous than we cannot somewhat agree on a number. A fair share of taxes must be definable enough to actually levy taxes. One picks a number, debate ensues, the number changes, marginal levels might be defined, contributions to the country are defined in a numerical manner, benefits from the country are defined in a numerical manner, other exceptions are decided upon, and one has a tax code. It is a long and laborious process. we end up with a tax code that is as fair as it can be in a two-party system.1
One can provide evidence that the concept of a fair share is nebulous by imagining that this message board needed money to stay online and that the money should come from users. Should everyone pay an equal amount of money? Or should there be a charge for every post instead of every user, and if so should there be marginal rates. Should lurkers pay money. Should all the money be raised by charging a fee for every day one accesses the board no matter how much or how little one uses in 24 hours. Should users suffering financial hardship pay less money. The only way to come to an agreement would be to set a deadline for taking the board offline, and even then the final plan might include a clause saying that this method will be used for one year and we will discuss everything again in 12 months.
And even that doesn't describe how nebulous a fair share is because we were working towards a fixed total. If there were an options to add features for more money and reduce features to save money, then the whole concept of defining fair share becomes an order of magnitude harder.
So. Yes I agree that it is so nebulous and that we can never find an objective standard for a complex system. But in the end we have to shoot for something.
(1) I will unhesitatingly acknowledge that the two-party system comes up with numbers very different from the case when the Libertarians and/or the Greens have a seat at the table.
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