I think you're looking at it from the other side of the river than I am.
My view is that there is a basic level of spending required to sustain living that shouldn't be taxed. -- The "poverty level" chart is as good a guide as any to define what that level is.
The only way to do that, without getting involved in the financial affairs of the individual or what they buy, is a blanket credit of tax that will be paid on those basic goods. Once the citizen has provided himself with the minimal basics of life, will the state get a share of his spending.
Since every citizen is eligible for the FCA, the prebate is not at the expense of another. It's a refund of your own taxes that you paid to buy those basic necessities.
This is an argument based on compassion, charity and social engineering, not fiscal basics. It is the same argument that any "progressive" tax scheme relies on. But it opens the door to all manner of government intrusion -- witness existing "sin" taxes and ponder how long it would take for "the people" to decide there was something wrong with Prebate money paying for those "sins". If the government gives you money, watch out, because they are eventually going to want control over how it is spent. Instead of a check, we might end up with a debit card that would only be valid for certain things -- groceries, "basic" clothing, etc. Sure the FairTax is not written that way now, but I can see it evolving that way because it has been all too easy to tax "sins" and "luxuries" in the past and get away with it.
Yes, it is an argument based on compassion. Although I think "ethics" is the better word for it.
Even under medieval land tenure, the serf was provided for by the lord during winter and the planting. Only after the harvest could the owner take his share.
The other two ideas that you mention "charity and social engineering"; can only come about if government is involved in your finances and your spending (like it does now). By broadly taxing all consumption and giving everyone a fungible check to credit the tax paid on the basics, you eliminate the main excuses for the state to meddle in the affairs of the citizens.
The limited "welfare" debit card is a possibility that we would have to contently watch-out for; there are (and always have been) politicians that believe the nanny-state should keep track of and control what the livestock citizens are doing.
"to constantly watch-out for". Furrfu.
[I think you're looking at it from the other side of the river than I am.
My view is that there is a basic level of spending required to sustain living that shouldn't be taxed.]
I see your argument. I guess I do stand on the other side of that particular river. I think everyone who is able bodied should contribute to the common good. I could be wrong, but I don't think the fuedal lord allowed the farmer to set aside what he needed for his family and only took his share of what was left. Even if a harvest was poor, the lord still took his percentage of the total. So that may not be as good an analogy as you intended. The lord's costs to provide protection did not change, and to allow his tenants to work no harder than necessary to provide for their own needs would have been a breach of the contract -- because without revenue the lord would no longer be able to provide the protection. A tenant under-producing time after time would have had his land taken away and given to someone more productive.
I think it is a psychological burden to people to have to admit they pay no taxes. Like they aren't carrying their weight when it comes to funding the common requirements of society. I don't think anybody would be proud to say "I paid $2,000 in taxes last year. But, the government check covered all those taxes. Didn't really cost me a dime. National defense ? I don't pay for any of that. Judicial system ? Nope, not that either."