“The Daily Stoic” e-mail is both odd and somehow typical of what is now normal morning reading in this year of the pandemic.

Not much more than a thought for that day, the Daily Stoic last week still helped clarify how to think about wearing face masks to hold down the spread of the novel coronavirus causing COVID-19.

The ancient Stoics of Greece and Rome, believers in virtues like courage and self-mastery, apparently admired the classical Spartans of Greece. The Spartans were hardheaded and militaristic, yet only soldiers who lost their shield in battle were punished by death, not those who lost a helmet or breastplate.

As explained in a linked post by the writer Steven Pressfield, the helmet only protected the individual. The shield helped protect the whole, tightly packed Spartan line.

You want to risk your own life, the Spartans reasoned, fine. But you can’t drop your shield and put the community at risk.

The Spartan’s shield is like a face covering in the continuing pandemic. It is less about protecting yourself than taking your place in protecting the whole community. Yet here there is generally no penalty for dropping your shield.

The only apparent sanction for not wearing a mask into a city-controlled building, as required by the mayor’s order, here in St. Paul is the threat of being asked to leave. That is not much of a disincentive.

There is strong evidence that it is possible to be contagious and spread the virus even if a person doesn’t think they have the symptoms of COVID-19 or the symptoms have not yet developed. That is where measures like wearing a face covering really matter.

The homemade cloth masks seen all over the Twin Cities won’t form a perfect barrier, but they are a big part of the strategy to contain the spread.

“Your cloth face covering may protect them,” reads the big type under an illustration of two mask wearers at the Centers for Disease Control and Prevention’s website. “Their cloth face covering may protect you.”

The CDC recommends wearing face coverings in places where maintaining at least 6 feet of social distance is “difficult” to do, “especially in areas of significant community-based transmission.”

The recent news on new COVID-19 cases here has been mostly encouraging. On the other hand, in the state’s reporting on COVID-19, investigators were unable in early June to specify how roughly a third of the people who had been infected in the community had been exposed to the virus.

When you think about the health of the group as a whole, wearing a mask makes perfect sense.

A low-cost way to reduce the spread of a contagious disease that causes serious illness and death would be good for a city and the state, and all the players in the local economy.

While not particularly comfortable to wear now that the sticky summer weather is upon us, cloth masks cost next to nothing. And with lots of people wearing them, mask wearers don’t have to fret about feeling awkward or out of place.

Not everyone will wear a mask, though, and it is not just a philosophical objection or a simple unwillingness to put up with the hassle. This kind of thing happens all the time.

This has been explored by thinkers maybe even going back to the time of the Stoics, the fact that it is hard to get everybody to contribute to something important for the group.

One of the best-known writers on the problems of getting everyone in groups to join in was Mancur Olson Jr., an economist from North Dakota who spent much of his working life at the University of Maryland.

One example: A silent auction to benefit the upcoming youth hockey season will still raise money if one player’s parents decide not to help. And the more people that get involved, the greater the chance some will let others handle the problem.

If nearly everybody else outside this week is wearing a mask, given the evidence that this practice restricts the potential spread of the virus, then the person who has decided to skip it will be getting a lot of the benefit for free.

There are only a couple of potential fixes to this problem. One is pretty close to the approach used by the Spartans, and that is simply to make everybody participate. Another idea is the government or some other organization offering an incentive to win the cooperation of the free riders.

Persuasion on the benefits of wearing masks may also work, or an appeal to civic responsibility, or simple home-state pride. It is unclear what kind of more tangible incentive would induce the reluctant to put on a mask, though ­— certainly not a financial one, since simple cloth masks are cheap and easy to either make or buy.

Delta Air Lines provides them to passengers in a free kit, one part of Delta’s effort to build confidence that air travel is safe and thus attract back more of its customers. Yet free isn’t cheap enough for everybody, as a recent story illustrates.

Delta apparently doesn’t want to be heavy-handed enforcing its mask requirement, so when one Delta passenger recently showed up at Minneapolis-St. Paul airport who declined to wear one, negotiations with a Delta staffer ensued.

The passenger finally agreed to put on a mask only if the pilot also was wearing one. Up walked the pilot and first officer, both wearing masks, and the passenger finally accepted the kit from Delta.

The Spartans probably wouldn’t have been nearly so patient.