People ask me what I mean by "public theology".
Public theology is the explanation of human society, social institutions and governments. If you a theist, it explains the existence of governments, nations and social institutions in God's plan. Even if you are not a theist, it explains the fundamental moral foundations of social life
Here is a statement of public theology that you may have heard before:
We hold these truths to be self-evident, that all men are created equal, that they are endowed by their Creator with certain unalienable Rights, that among these are Life, Liberty and the pursuit of Happiness. — That to secure these rights, Governments are instituted among Men, deriving their just powers from the consent of the governed.
From the Declaration of Independence, of course. It is a statement about the nature of humanity (that it is men, that they are equal, and that they are given rights by God.) It is also a statement about the origins and purposes of governments (that they were "instituted among Men" through voluntary agreement, to secure those rights.)
The public theology of the Declaration of Independence, or the Enlightenment as a whole, is a decisive break with prior understandings of humanity, social institutions and government. Just saying that governments are human creations, rather than the work of God is a break.
It is predicated on a theory of a "social contract", the voluntary creation of a superior power through the agreement of free men. If you think about it very closely, the story of the social contract is as much a myth, a fairy tale, as the story of Adam and Eve in the Garden of Eden.
The evidence is that small group structures, the extended family, the band, and clan are as instinctual in us as prides are to lions and hives to bees. But beyond the small group, larger forms grew, not from mutual agreement, but by the demand of the powerful that the weaker submit.
[Side Note for future exploration: the story of the origin of our churches and congregations is also rooted in a myth of voluntary agreement among equals. Just sayin']
Contemporary liberal public theology is now breaking from the liberalism of the past, which has always pointed back to a time of freedom before the social contract was made. The old liberalism asked the question: how do we limit this power we 'have instituted among' us so that each of us are maximally free. The old liberalism is the new conservatism.
To us, human history is not a story of a fall, but is a story of evolution. We are moving from a cruel, oppressive, hierarchical, and deprived past towards a future when more people have agency, more people are treated equally, more people have what they need, more people live in safe and secure societies of peace. We advance as a whole, as a species, through increasing cultural complexity.