People often will answer the above question with a list of things the government should *do* (operate courts, etc.), but these usually circle around the actual answer to that question. And obviously people will give many answers to it. 

My answer, after my years of thinking about it in different ways, is fairly simple:

The function of government is to provide the services, capabilities and resources to perform tasks that, for one reason or another, individuals and private enterprise are incapable, or ill-suited, to reliably provide.  

By its nature, the precise tasks the government should perform will vary depending on the size and nature of the governed region and population (and, indeed, by the available technology -- if you go back in time you'll find there's some very different constraints on both private and governmental ability to act than there are today). 

Today, here in the USA, we're dealing with a truly MASSIVE country in multiple ways. Our population is heading up towards four hundred million people -- as many people as there were in the entire world only about 800 years ago. The continental USA is close to three thousand miles across and a couple thousand or so North-South, and covers terrain and biomes of nearly every description. Economically, despite Trump and company's current attempts to blow it up, it's still one of the most powerful economies on the face of the Earth.

Moreover, socially it is, and has always been, a clumsily-assembled patchwork, made of everything from religious refugees to slaves and their descendants, the Native American survivors of dozens if not hundreds of different tribes and tribal networks, former slaveowners and abolitionists, Irish famine refugees and Europeans fleeing WWII, and many others. The elite designers of our Constitution, flawed as they were, at least were smart enough to steal ideas from the best (the Iroquois) and add their own, trying to create a structure that would serve to create a country somewhat better than the ones they left behind. They... sort of succeeded -- which is, to their credit, about all that ANY small group of people could be expected to do, especially when they can't benefit from our 200+ years of hindsight. 

This socioeconomic "patchwork", however, is a large part of the reason we see our current problems. To a great extent, the conflicts we see are not just racism, sexism, etc., but basic philosophies in conflict -- ones so basic that they are rarely actually taken out and EXAMINED by the people who adhere to them. 

The answers to a few relatively simple questions can reveal these divides. 

1) Are human beings of inherent worth?
2) What are the limits of an individual's rights? When can another individual, or a society, restrict them?
3) Do individuals owe anything to the society in which they live? Why or why not?

From my point of view, these are the answers:

1) Yes. We are the one species we know of that is not only sapient and self-aware, but inherently able to imagine the worlds that could be, but are not -- meaning we can create or destroy in ways that no other creature we know of. I believe that, to quote one of our classic founding lines, all human beings are endowed with certain inalienable rights, including life, liberty, and the pursuit of happiness.

2) Put simply, one individual's rights are limited whenever and however they come into conflict with other individuals' rights. A society, being a collective of individuals working towards a presumed common good (or at least stability) or another individual may restrict individuals' rights when the actions under those rights would harm others. (more complicated questions arise about judging harm on one side or another, but that's detail work, not basic principles)

3) Yes, absolutely. Even if you have a terrible, sucky childhood here, you're still in a setting that has resources and capabilities that you simply could not ever get for yourself. A single library is the accumulation of knowledge of centuries. If you continue to live in the society, you owe something to it, even if you owe nothing, or less than nothing, to specific individuals within it. 

There are some other similar questions and answers, but these suffice as a start. The problem, as I mentioned earlier, is that a lot of people don't really think about these things -- which means that not only may they not know their answers, but they may act in ways contradictory to their beliefs in one or more areas because it suits their particular preferences or needs in another context. 

So let's look back at those three rights, Life, Liberty, and the Pursuit of Happiness.

To me, it's intuitively obvious that you have no right to life if preserving your life is not in your personal control. This includes anything that's essential to life -- food, clothing, shelter, medical care. People who want these restricted or "means-tested" are, implicitly, saying that not EVERYONE is of inherent worth -- that some people don't deserve to live. To me, it's also obvious that the basic level should be one on which the recipients are comfortable; not some fabulous lifestyle, but not eating beans and rice every meal for months, not wearing terrible shoes and worn out clothing, not living in a house without sanitation or refrigeration or heating and cooling. At a level, in short, where they can quietly enjoy the life they have. 

You have no liberty if you are restricted from doing anything you might like that won't harm anyone. In a large society, of course, "harm" can come in a lot of forms, concentrated, diffuse, physical, social, economic, and the society and other individuals have the right to draw the lines there. But things like "I want to marry a person o fthe same sex" or "I want to watch this movie that someone else doesn't like" or "I want to wear this traditional clothing of my people without being bothered" don't harm anyone, and shouldn't even be a matter of question. The questions come in when you say, instead, "I don't want YOU to do these things because I don't like them". 

The Pursuit of Happiness is the most nebulous of them, but to me it's again fairly clear: a person can't really "pursue happiness" if they lack the time, resources, and freedom to do so. They should not be driven to work so hard that they cannot relax and enjoy life; they should have time to themselves and their friends and family. They should have enough spare resources to allow them at least some basic choices of luxury and entertainment. Otherwise, they can't "pursue" happiness, let alone attain it. 

A lot of people who may oppose these viewpoints are often doing so because in their gut they believe -- they WANT to believe -- that success comes from effort, that happiness is achievable by those who reach for it, and that the world is FAIR. And therefore, if someone's getting all that stuff without what they see as an appropriate amount and type of effort, it's Not Fair -- it's cheating at the most basic level. Maybe even it's theft, stealing the benefits that someone else could have gotten if they worked for it. 

This strangely idealistic concept is, unfortunately, one of the causes of some of the worst actions of our society, because such people will work extraordinarily hard to prevent any such things from happening -- often even if it costs them a great deal. For instance, drug testing for people on various government programs has essentially UNIVERSALLY shown itself to be hideously expensive -- it costs much more to do all the testing than it would to give the very few people actually on drugs the benefits anyway -- and it creates barriers for even those who "deserve" the support. 

If you accept that all human beings deserve their basic rights, these problems disappear; there's no need to waste money testing because everyone has the same rights. 

"But the cost!" is often one of the major arguments; the problem with that argument is that often it's the BARRIERS that cost. The American "healthcare system" is a prime example. The insurance company setup effectively DOUBLES the cost of our healthcare; providing Medicare for All without any gatekeeping would improve our country's health while cutting the actual cost of healthcare in half. 

And it's more than that; ensuring everyone IS taken care of on a basic level ultimately benefits everyone -- by reducing the cost of emergency care, of patchwork solutions to ongoing problems, of stopgaps that simply don't solve the problem. 

There's more to say on all this, but it's late and I've got to stop for now.