In Ann Arbor, I live with 121,000 strangers. Together, we live among 10 million strangers in the state of Michigan, 332 million strangers in the USA, and nearly 8 billion strangers on Earth.

I don't mind doing favors for my friends and loved ones, or even for one of the 8 billion strangers if I happen to be face to face with them. I even like it. It makes me feel good to demonstrate, for the benefit of those present, the fact that we live in a society where most people are basically benevolent toward strangers. I also feel happy to see the other person feeling happy, or at least less stressed. These small pleasures have entrained a habit in me, over the course of my life, to do small favors almost automatically. When the stranger I have helped says "thank you," it means something to me.

But I've also noticed that I don't always feel that way. Sometimes, I notice my automatic consideration for strangers causing me to help others in ways that they'll never notice or appreciate. Sometimes, the people who do see get angry at me for it. For example, if I ride my bike to work, to keep myself fit so that I can do my job well, avoid getting sick in a way society will have to pay for, and spare the planet some CO2 emissions, sometimes drivers get randomly angry at me. And I'm not a bad bicyclist - I go with traffic, in bike lanes, wearing a helmet, with lights on my bike, stopping at stop signs.

I also read quite a lot of scientific literature. We want a scientifically literate society, which is why we teach about science in school. Sometimes, I learn things from my reading that are relevant to a conversation I am having. It's rare that I talk to strangers about what I read, unless those strangers are scientists themselves. But I've noticed that sometimes, when I tell my loved ones what I read in the study, and it happens to contradict what they currently think, they sometimes start acting a little more like a stranger for a while. You might have experienced this yourself, perhaps at Thanksgiving, if you celebrate.

As a third example, I lined up early and eagerly to get vaccinated. It wasn't easy to figure out how to get boosted, but after making a lot of phone calls, we found a CVS that would do it and waited there for a couple hours for our shots. It was a strangely joyless situation, with a bunch of strangers, lined up in an uncomfortable, fluorescently-lit CVS, not talking to each other. Yet we were doing a favor on behalf of all of society, protecting each other from a virus that was all to eager to make the transition from stranger to our closest friend. Before we got boosted, our unboosted status was treated by our families as a slightly negative, anxiety-provoking state, even though we had no control over it. After we got boosted, there was no joy or appreciation, just a moving on to the next thing.

These examples make me unsurprised that so many of the strangers around me do not choose to bike to work, read scientific literature, get vaccinated, serve in the military, vote, donate hair or blood or a kidney. 

Even good families only rarely say "thank you" with the sincerity and consistency that is warranted by the virtuous acts they expect of each other. Cities, states, countries, and the planet as a whole are even worse. When I read "thank you" email messages from my university, or from corporations and government officials, I delete them without reading, because they're crowding my inbox. I feel from neutral to negative about these messages.

But I've never felt bad about receiving a gift of money. It's not impossible for me to imagine situations where I would feel bad about the money, or people who'd feel uncomfortable about receiving such a gift, but that would be unusual. Money is hard-earned. If somebody gives me money, I know for sure that they have made a sacrifice. Whatever the message behind the money, they really meant it. Money is also potent. It never makes my life worse to receive a gift of money. In the worst case scenario, where I felt bad about accepting the money, I could donate that money to charity, where the ultimate recipients are likely to greatly appreciate a gift that was doing no good for me.

I think we should stop worrying about the possibility that paying people for doing good things on behalf of society will make us less altruistic. We still have our friends and families and chance encounters with strangers, where the exchange of "please" and "thank you" will continue to give us practice building the bonds of emotional empathy that we value.

But I know that there are hundreds of millions, even billions, of strangers making sacrifices, large and small, on my behalf. They're riding their bicyles, lining up to get vaccinated even though they hate shots, donating blood or a kidney. I can't say "thank youo" to them personally, and neither can almost any of the other recipients of their largesse. They don't need their email inboxes crowded with a "thank you" message, and they don't need a billboard with "thank you" plastered over it ruining the view. 

What we can do is build infrastructure to say "thank you" to all those benevolent strangers in the form of money. We can pay them a reasonable sum for doing us the service of donating blood or a kidney, for getting vaccinated, for using less gasoline, for staying off drugs, for voting. In some specific cases, there might be reasons why this is too difficult, but in others, there are already thoughtful plans on how to accomplish this. We should put them into place.

I would like to live in a society in which creating a way to give money to strangers in exchange for pro-social behavior was viewed as a higher order of altruism, or of politeness. Where it would be impolite for us to ask each other to get vaccinated for free, vote for free, donate blood for free. Where voting in a program to make such payments is viewed as a way of a city, state, country, or world full of strangers saying "thank you" to each other for making the world a better place to live.