These arguments are obviously made from a theoretical standpoint and there are always complications when applying them to a real live society. But to further complicate the validity of their application: when these theories talk about individuals, they really mean adults. Where do children fit into the equation?
Spending on children comprises one of the lowest federal expenses. The US government spends about 2.2 percent of the GDP on children and various services directed at them. In comparison, about 5.3 percent of the GDP is spent on the elderly.
The view from the budget is even more shocking: less than ten percent went to children; more than a third went to the elderly.
Since 1975, spending on children has only risen with inflation and Medicaid costs, whereas spending on the elderly has skyrocketed. Benefits for children — paid through their parents — have shifted away from cash payments to in-kind benefits, through initiatives like food stamps, health care and programs such as Head Start. But within the next decade, spending on children is actually expected to decline.
This seems like an unequal split when viewed with any philosophical lens. The economic state in which children live is, in nearly all cases, irrespective of the choices they themselves have made. A child's opportunities are determined by the sheer chance of where they are born and to whom. An older person, however, has had a lifetime of choice-making. Sure, everyone is entitled to a little assistance when they can no longer care for themselves, but from the libertarian perspective — perhaps they should have made better choices in their youth to ensure a more comfortable future.
From the Rawlsian perspective, why should one age bracket be given significantly more assistance than another? Where's the fairness in that? If resources are not private, but rather societal, shouldn't aid be spread around equally?
If "inequalities must work to the greatest benefit of the working poor," it doesn't seem that this particular inequality meets the philosophical bar. Subjecting children to poverty, despite the happenstance way in which they found themselves impoverished in the first place, is unfair on all counts.
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(1) (2) Tomasi, John. Market Democracy, chapter 6