He's failing to distinguish between (1) "I love my children and am very glad to have them and would be very upset if they were replaced by different children" and (2) "My children are in some absolute sense the best children there could possibly be, and if they'd been different I wouldn't love them and be so glad to have them". #1 is normal and reasonable and sensible and nice. #2 is batshit insane.
I think a similar error is behind some people's alarm at the idea that the existence of physical disabilities is a bad thing that people might try to do away with ("do you want to do away with my sister, who has this disability?").
And I think a slightly less similar error is behind the repugnance of Derek Parfit's "repugnant conclusion" (you can start with some natural assumptions about what makes the world a better place, and end up with the conclusion that our world is less good than an alternative with vastly more people, all of whom have lives that are just barely worth living -- but what "just barely worth living" means is not "if they were slightly worse the people whose lives they are would prefer to be dead" but "the world is better for their existence, but only just").
None of the above has anything much to do with regret, but I do also think there's something wrong with how Caplan is thinking about regret. But I think the mistake described above is the really big one.
Doesn't he distinguish between (1) and (2)? From the article:
Like most parents, I have a massive endowment effect vis-a-vis my children. I love them greatly simply because they exist and they're mine. If you offered to replace one of my sons with another biological child who was better in every objective way, I'd definitely refuse.
Bryan Caplan in Parenthood as the Trump of All Past Regret explains: whatever tiny alterations he makes to his life before he had his children, would result in him not having the precise children he has today whom he so dearly loves, and therefore he does not regret a thing.
This is seems to me like an entirely wrong use of regret. I think regret is useful when it suggests how you could have done otherwise, when having different such behavioral policy consistently leads to better results in structurally similar situations.
It's not exactly like the mistake of thinking that chaos theory should suggest you pay attention to every little thing in life. There the mistake was to think you could reliably and precisely enough predict how the little things being different leads to outcomes being different. Bryan is thinking about a very specific outcome in his life which he already knows has come to pass. He is counterfactually considering how it would not have been if everything in his past were not exactly as they were.
But given determinism, everything is already decided. This does not rule out free will, but it does suggest a proper use for counterfactuals. According to Vladimir Nesov: The meaning of a thing is how you should be influenced by it (the most succinct expression of LW philosophy imho). According to Gary Drescher: Why should you consider alternatives when making a decision, given that your ultimate actions are already determined? Because counterfactually-speaking if you did not consider such alternatives, you wouldn't have decided the way you did. So the use of counterfactuals, and in particular regret, is for us deciding how to behave. I don't see how Caplan's regret makes use of this.
And of course, there are other aesthetic uses to counterfactuals. Fiction, to take an obvious example. But am I missing something here in thinking that Bryan's regret is quite useless?