public buying and selling,....."
I am of the impression that although most Trads would agree that we should try to refrain from unnecessary buying at department stores on Sunday many of them find nothing wrong in buying tickets to entertainment events or to buying a meal on Sunday when it is not necessary. It seems to me that by doing the latter we feed into the secular culture (which profanes Sundays in every way imaginable) by treating Sundays like any other day of the week.
Public buying and selling is generally not permitted ON ITS OWN. But it's permitted when done in support of NECESSARY activity. I can purchase medicine at a drug store. I can purchase a meal at a restaurant.
Yes, the logic for entertainment is a little bit weaker. Eating is NECESSARY. Entertainment is PERMITTED. Labor is licit in support of necessary activity. Is labor licit in support of PERMITTED activity? To me, since the entertainment isn't necessary, by extension the work done in support of it is likewise unnecessary.
It's like the one theologian I read who said that it's OK to drink beer between meals on fast days ... because it's a liquid. But, then, he says, it's OK to munch on some snacks with it ne potus noceat
, so that the food doesn't cause harm (e.g. upset your stomach ... due to drinking on an empty stomach). That's such a huge stretch. My brother (also a seminarian) and I used to joke that I could go drink a beer and then eat a Big Mac with it ne potus noceat
. We'd toss that phrase around as a joke ... rather mocking this particular theological conclusion.
Another theologian said that something was considered drink (vs. food) if you could get it through a straw. So my brother and I joked about blending up solid food and sucking it through a very fat straw.
I once also read a particular theologian who used tortured logic to declare that if a priest did not offer Mass on Sundays he was not required to ATTEND Mass to meet his obligation to keep the day holy. That's because the Church law requiring Mass attendance was, technically speaking, addressed to "the faithful" and not to priests.
Jesuits were notorious for this kind of reasoning. There's actually a term for it ... "Jesuitical logic" or "Jesuitical argument". In doing so, they completely undermined the spirit of the law. Not only that, they made Catholic moral theology appear very Pharisaical to the world. I think they did it just to show how clever they were.