So Brian, your definition of "common good" is something that benefits everybody. Does that included roads, bridges, dams, etc? An awful lot of people don't benefit by that stuff.
But G makes the salient point. Raising healthy kids benefits EVERYBODY. If you're in doubt, check out the countries that have declining numbers of children. China comes immediately to mind. Their population dynamics are taking them over a cliff. Europe is in the same boat, as are we.
So yeah, child care benefits the "common good".
OTOH, the military is a LARGE make-work project; basically welfare for millions. Every item they make is designed to be blown up or otherwise destroyed. No lasting infrastructure.
I do get the need for the military. But we might want to tone it down a bit. Diplomacy is WAY cheaper and longer lasting.
But Trump's diplomacy consists of threats, intimidation, etc. And at the same time he's asking for ANOTHER $500 billion bump in yearly military spending, along with the specific aim for no new taxes. That means a direct transfer of gov't program expenditure into the military. Guess where THAT comes from? EPA, Park Service, food stamps, early child education. You get the picture.
This is Project 25 stuff writ large. The true conservative Libertarian approach to gov't, a la the Koch's. Basically the gov't doesn't do anything except the military and a few very large infrastructure projects. All else is privatized.
Time to get rid of these clowns.