If you made tolls on a toll road optional, the road owners would not be able to keep up with maintenance, yet I think most drivers value the road...

So what's this 'road' in your analogy that was installed by the union, that wasn't there before, and that introduced a lot of utility, comparable to a road?

The implication in the comment I was replying to was that if people see the value in something, they will voluntarily contribute to its maintenance.

The fact that many workers would not pay optional dues does not prove that the workers don't see value in the union.

Obviously the purported value of a union is in the ability to collectively bargain on behalf of its members (and to provide tangible support for workers participating in strikes or who are pursuing legal action against an employer). Unions may do this or not, but the argument that gp made is not a good one.

It's a hilarious tragedy that the person you're responding to has the definition of 'tragedy of the commons' backwards in their mind

It's actually a decent comparison, because a large percentage of the cost/benefit is building the road/union, and comparatively little is the maintenance. But the tolls/dues remain the same across.

No, it's because if dues were optional, the only game-theory-efficient outcome is that no one pays dues.

If dues are mandatory, The only game-theory-efficient outcome is that the union takes as much money as possible and provides as little benefit as possible.

So a business

The tragedy of the Commons is when there is a public good that, if most people contribute, everyone gets back more than they put in, but because it's rational for each person independently to not contribute (since it isn't strictly necessary for them in particular), it fails to happen.

You know, like not contributing your Union dues.

> If their members were really convinced of the value that tragedy of the commons wouldn't occur.

It’s called a Tragedy for a reason.