I've finally finished reading Papal Economics, a lot got in my way in the mean time. The final part of the book dealt with the main argument Fr. Zieba had been building to- that a knowledge of Original sin leads one to endorse regulated free markets under democracy- for the simple reason this forces those embroiled in Original Sin to provide work for their neighbors while satisfying those temptations to sin.
This is true as far as it goes. But I go a step further.
People are more likely to sin in an anonymous relationship than in a personal relationship, and the chance of sin goes up with the number of relational links in the transaction chain.
In other words, two neighbors or family members that have to live with one another have a very low probability of force or fraud entering into a transaction. Two strangers meeting in a local marketplace, is still extremely low, because they might have family or friends in common, living locally to where they were born.
A large scale city that attracts immigration, the probability of force or fraud being used in a transaction goes up, in relation to the anonymity and separation of the participants in the transaction.
Trade between states within a country's borders gets harder, because one has to appeal to the national government to resolve disputes, and because the chance of being able to affect the life of somebody committing fraud or force in a transaction is extremely small.
International trade gets very complex very quickly, and there is no jurisdiction or control over the marketplace at all. Laws stop mattering, and the chance of somebody who wants to commit force or fraud being punished for it is very small indeed.
The knowledge of this is almost instinctual- and is the reason why if you track actual money usage through transactions, natural autarkies appear rather quickly. If we took advantage of this, perhaps we'd even be able to build the distributist paradise that has appeared in the wake of its lack of a food market caused by the collapse of communism.