Volunteer labor is a thing. That’s how many cathedrals were built.

If you volunteer enough, your salvation is all but assured.

Doesn't exactly sound like volunteering to me.

As a matter of fact, at least here in Germany a lot of cathedrals took decades, some even centuries to build - the Cologne Cathedral, for example, took way over six hundred years. Additionally, they were often built in "batches" and expanded and modified, schedule pretty much depending on some emperor or volunteer donations providing enough funds for the next section.

Me and my s/o, who actually studied a lot of the German cathedrals for her master's degree, went on a tour across a lot of the cathedrals this summer with the 9-euro flat train ticket... it's utterly amazing what medieval people could pull off. If you're interested in old buildings, wait until the successor of the 9-euro ticket comes next summer and go on a trip yourself, it's definitely worth it.

Just because there's something in it for them doesn't mean it's not still volunteering.

Do you also apply such a standard to modern examples of volunteering?

Sadly, I posit that that is the modern definition of volunteering. Doing something without getting paid, typically means no monetary value. And since money is fungible for value in general, it means doing something where you get no value out of it. And there is obvious value in salvation.

That said, I think this is just a misalignment in what "volunteer" means. Historically, it was more like "volunteer trees", in that you didn't specifically recruit or hire them. It did not mean that they did not get benefit out of it.

Cathedral builders were among the most sought after, and highest paid, workers and artisans in medieval Europe. They had de facto unions, free week ends, limited work hours and basic health care. They could enforce that because there were only so many qualified people to build cathedrals back then.

Servitude labour was more of a thing for castles, Cathedrals were build in towns and cities, with free citizens. Castles were build by nobles and those had servitude populations to draw labour from.

This is... probably misalignment with modern definitions. Volunteer for the time was not at all the same as what we think of today. To wit, many of the "volunteers" were as likely getting the only form of compensation that they could get by being there to build something.

Specifically, if there was a local market, it would have been near the cathedral. And if you didn't have a reliable farm or other plot of land to provide food, seems reasonable to assume your best bet was to be compensated in some form for manual labor.