I’m thinking aloud here, but maybe you could help him spell out the consequences of his actions. It sounds like you’re the one that owns or rents the place, and you also mentioned food. So maybe charge him a fair market value for rent and food that you’re purchasing.

Then when he doesn’t have enough money, you grant him a monthly subsidy to make up for it. The subsidy is the amount you’re paying for your children to not suffer and because you love him. The hard part is then to come to grips that the subsidy is not infinite. Tell him that.

I realize we’re talking about the value of your children’s suffering and the value of your love, but you don’t need to have a concrete number. Like in the article, you can start to set upper and lower bounds. Like if it’s $10, that’s no big deal since your love is worth more than that. If it’s 1,000,000 then maybe your children would be better off with the opportunity that money could buy… Then work your way down or up. Again, you don’t need to actually arrive at a number. But maybe it will drive home the point that you’re not made of infinite money and his financial autonomy has exceeded his capacity. Maybe it’ll be a wakeup call that he’s not just affecting himself with his poor decisions, it’s costing you and your children.

Or maybe instead of a subsidy, make it a loan. Charge him interest. It’ll be like forced savings.

I’m thinking the subsidy works better, mainly because it’s simpler. And being a loan collector is hard.

Yeah, astute question. I have no idea how to extend this to larger groups (like libertarianism tries to do) or even to pairs of people both of whom aren’t fully trustworthy.

This is my problem with libertarianism as well. It’s all fine and good to cut taxes and move services to private, fee based systems; but if one does this then don’t go crying when your house burns down because you couldn’t afford to pay the fees.