The thing with economies is they really are zero-sum on an instantaneous basis. There's also a deep dark secret that there is really no such thing as real debt when it comes to national or international levels. What I mean is this:
At any given moment in time, the sum of all production of goods must equal consumption (which includes breakage) plus rate of change of stuff in storage. Similarly, the rate of production of services must be equal to the rate of consumption of services. (That is, you cannot "store" a haircut - haircuts must be consumed simultaneously with their production.) (NOTE: education is a little fuzzy - education is kind of a "production capability storage" - it could probably be considered a type of production, where you create and store the ability the perform work, but that capacity does decay if it's not used.)
Debt is simply an agreement that use of a good or service now must be exchanged for a good or service in the future. The "non zero sum" aspect of economies is that sometimes you can use current goods and services to increase productivity, so that in the future you can make more goods and services with less inputs.
When it comes to sovereign debt - it's mostly just an accounting gimmick because there is never going to be satisfaction of that debt. One idea behind sovereign debt is that you can direct the use of current goods and production by creating debt (agreeing to pay someone for current production in the future), and the benefit of fiat is that you can create that debt without having to have someone mine a resource. This works fine so long as the current production goes to things that improve productivity. It does not work if it goes to things that do not improve productivity.
This is the unstated root of all the political discussions. Some people think that spending on X will improve productivity, others think it will not. As a society, yes, we want to be able to keep people healthy and happy because in general happy, healthy people are more productive (and yes, you do have to have some minimum level of societal productivity to make society function). As soon as you start spending not on productivity, though, the system falls apart - eventually people don't believe that the debt will be honored in the future, so they change their current behavior by producing less and/or hoarding or violently protecting what they do have.
So the arguments about UBI are very interesting - it involves a combination of cultural norms and economic reality. The cultural norms are related to the portion of one's work that is expected to be retained versus shared with others. The economic reality is that you can't give away more now than exists now. This is why I have suggested that UBI not be some fixed number as most propose, but rather an honest, transparent wealth redistribution scheme - because really you have to redistribute what exists, not make something up.