In economics, a public good is a good that is both non-excludable and non-rivalrous in that individuals cannot be effectively excluded from use and where use by one individual does not reduce availability to others.”
From Wikipedia, Public Goods
I believe this standard definition of public goods assumes something most definitely not in evidence: Whether a given “public good” actually is a “good” to all those affected by its existence. In any state of human affairs there will always be those for whom a given good is, on balance, not “good”, however non-rivalrous and non-excludable it may be.
Let us consider that old favourite example of ‘The Roads’, which in a given case are far from “good” in the estimation of the farmer or the owner of a nature preserve whose land is taken under Eminent Domain against his will. The former property owner, whose land was taken from him by force of law and threat of punishment, may not be excluded from using that land in its new role as a road, but he is certainly precluded from using it as he would prefer. On balance, for him this road is not a “good” at all, not even if it means a quicker trip to St. Louis or Seattle. And it is not only the former owner for whom the road is not necessarily a “good” on balance. Anyone who lives near it, within sight or sound of it, may find it a dreadful incursion on his view, or on his peace and quiet, or even on the relative unlikelihood of his being burglarized or murdered by itinerants using it.
Or take education. Now if a man says “education is a public good” without making any specifications whatsoever as to what he means, he might get by with that simply because, absent specification, people will mostly interpret “education” in some sense already in line with what they want it to mean or believe it means. But speaking of the real world rather than of abstract umbrella terms, education takes place only in specific instances, in concrete times and places and circumstances. If one is speaking of any education other than self-education, it is not non-excludable, since there are always entrance requirements that must be met and rules of conduct which must be followed if the “non-excludable” student is not to find himself excluded. And since time and resources are finite, not everyone can be accommodated in any given learning environment (not even that of the ad hoc pub discussion among friends or the meeting of the book club), hence attendance at the “school” is far from non-rivalrous: some who would participate are accepted, some are not. So in the real world education does not meet the requirements for being a “public good” because of the excludable and rivalrous nature of nearly all establishments providing it. Neither is education a “good” in the minds of members of the public when what is taught is in their judgment untrue or perverse. (How many of us are in love with the leftist/socialist/fascist drivel taught in colleges and high-schools and even right down to kindergarten? Do we consider this education a “good”?)
A final, and very specific, example: The Watts Towers in Los Angeles, constructed as a hobby by Simon Rodia, an Italian immigrant, over the course of decades. After his death there was a big brouhaha, because Los Angeles had condemned the property, and some Angeleños thought it an eyesore and wanted it torn down instanter, whereas others admired it either as a work of art or as a piece of local history or — maybe — even because they believed in property rights. So are the Watts Towers a “public good” because they are non-excludable and non-rivalrous? Or do they fail to be one because not everyone considers them a “good” in the first place?
Actually, the only “public goods” that I can even make a case for are breathable air (not very toxic beyond the extent that Nature provides anyway), reasonably safe drinking water, and some reasonably hygienic ways of disposing of sewage and other toxic waste. Aside from these, the proper functions of government — protection of individuals’ persons and their property — may be legitimate “public goods”. But this is really an abstract idea, and the devil and any “public good” derived from it, is in the details.