To me, there are several arguments for progressive taxation.
To begin with, the wealthy benefit disproportionately from the playing field we have -- our robust marketplace and ample infrastructure (underfunded, though it may be). The further you are from subsistence, the more opportunity you have. In a very real sense, we're not actually a liberal society when so much is pay-to-play. So one argument for progressive taxation is that it's a means of rebalancing opportunity when wealth and income are grossly unequal
But I'd go further and assert that our means of wealth allocation is by no means fair, a priori. In fact, it's increasingly unfair. From that perspective, progressive taxation is a patch on the problem.
This would be a socialist defense of progressive taxation, but it's also possible to justify from a capitalist standpoint. If it's true that the wealthy are rewarded in return for their contributions to society, well then we should put them on a treadmill to keep them working. This is how corporations treat labor, after all. Unless of course real world capitalism is only for the benefit of people that happen to have capital.
Many!
There are 2 very different spheres of discussion the value and effects of taxation: morality, and economics.
From a moral standpoint, it depends on which system you abide to. In utilitarian terms, the case for higher income to the rich would be that the rich would suffer the loss of income a lot less than a poor man: someone with 1000 dollars would greatly suffer losing 500, but somone with 10 million, would not suffer for 50,000. You could argue in utilitarian terms that taxation could go very harsh in this regard, but then you know there will be some negative consequences (people leaving, etc) which can make it complicated.
In libertarian terms, self-posession and private property is paramount. What you have is yours, and whoever takes it is committing an act of robbery and violence. Any tax is an application of force, so not only progressive taxes are bad, any tax is bad. There shouldn't be taxes, they should be voluntary.
It is deontological to think that the taxes which are levied on richer people are a must because of the duty the rich have to the poor. A layman could think it is his duty to remove as much from the rich in help of the poor, even with the application of force.
To which system you subscribe, you will have a different opinion of the matter, but may I add that each person is a part each system and what we are the most is inconsistent.
In terms of economics, which of the above moral systems, utilitarians would care the most, you will find disagreement. There is a case that the rich paying more taxes ends up meaning less investment, which is what increases productivity and overall wealth, also known as supply-side or "trickle-down" economics. On the other side, you have increasing government spending to perpetuate and increase demand and produce growth. (keynesian economics).
Would government spending reduce or increase poverty? would it help or damage the economy?
Is an economist team thinking up this tax? or is it a group of politicians fattening their budget? It's almost certainly the latter.
How is it fair that a low-income family of four makes $40,000 combined and pays $24,000 in taxes (60% of their income), where a middle-class family of 4 earning 200,000 a year pays $24,000 in taxes (12% of their income), while wealthy family of 4 earning 2,000,000 a year only pays 1.2%.
Does that seem "fair" to you? I don't think it is. In my own view of society, there is a certain amount of wealth distribution where we admit that some people will be lucky and some people won't, and that in capitalism, we will ALWAYS have winners and losers. The winners shouldn't have to give up all of their worth (be able to reap the rewards of their savvy), but the losers shouldn't be abandoned by society, either.
There are plenty of arguments to make for and against "fair," and "unfair," taxation. Paying according to your means seems fair to me.
of course, one could reasonably make the argument that like many things in life, taxation isn't fair, and yes, you might need to only buy a BMW instead of a Rolls Royce so that someone can afford food.
It's really simple. Occam's razor it. Take the cynical view, and figure out what someone proposing would gain from their proposal, vs what it would cost them and others. Offer a solution that would not benefit them, personally, as much, but would include more benefit for whatever else they're claiming they support. See how often you're taken up on that offer.
This cynical view has successfully managed to keep me from being infected with many of the most virulent memes of our time, like Bernieism and believing that lives matter. It's also protected me from the many, many women who want to sap my precious bodily fluids.
/self parody
I.e. Costs of daily living may eat up 90% of a person on $30k a year's income whereas they may only be 30% of a person on $120k.
Therefore most progressive taxation systems offer an income free tax bracket. In Australia this is around 20k now; so up to 20k you pay $0 in tax.
That acts to protec the living standards of those on low or minimal incomes whilst providing tax revenues that allow the government to supply the services people on higher incomes need to generate their higher incomes (roads, rail, water, safety etc)
Even as a 'non-rich person', I can't help but think that progressive tax rates are unfair.
For me, fair means treating everyone the same. Regardless of everything -- that includes income.
Given this assumption of what fair means, the only fair tax system would be for each person to pay $X per year. A Family of 4 would pay 4 * $X. etc.
Can someone else offer a better definition of what fair means? And why I might be wrong?
I realize this would put a large burden on poorer folk in order to maintain the same tax revenue we have today. That may be undesirable. In fact an unfair tax system my be the more desirable tax system of the two. But even something good and desirable may still be unfair. I think that is the case here.
I think we may need to better separate good from fair in common language. They're intertwined, but they shouldn't be IMO.