# Humans are (mostly) metarational

At least in the early days of LessWrong this community was mostly focused on all the ways Man's reasoning failed him, the myriad ways we are irrational. What foolish humans, making mistakes even trivial mathematics can show you are wrong!

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Evolution aims to maximise number of offspring. But people don't have a direct drive for that because encoding that into a human brain is too complex. Instead we like sex, which in most environments is a pretty good proxy, albeit with the occasional extremely embarrassing screwup. In a sense we have a meta-drive for offspring, which manifests into myriad actual drives which leads to a good enough approximation of the meta-aim.

In the same way, people aren't rational, but if a rational person were designing humans they might very well program us to make the mistakes we do, all in the aim of rationality. You see, we might not be rational, but we are meta-rational!

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You decide to build a shed. You're a novice at carpentry but you set to it with gusto. This shouldn't take too long! 2 months in though you're still only half way through - everything seems to be taking far longer than you expected!

If you had thought from the start it would take 2 months to build the shed you wouldn't have bothered. Now you think it will still take another 2 months but you're reluctant to abandon the project. Foolish human! Have you never heard of the sunk cost fallacy?

Except it isn't!

- If you choose to leave the shed for now, then building it later will take you the full 4 months. Completing it now will only take 2. You have a unique opportunity to build the shed at half it's future cost, and should weigh that before throwing this opportunity away.
- If you choose to buy a shed you'll have to pay for the cost of the materials you already bought + the cost of the shed. At the start buying a shed would have saved you the cost of the materials, making it a better deal.
- If you abandon the project now you'll still have to dispose of the half built shed somehow.
- You've already discovered a lot of the pitfalls involved in shed building. Your time estimate of 2 months is more precise than it was at the start.

Now I agree that there are contrived cases where the sunk cost truly is a sunk cost, and humans still make the same mistake. But in the real world the fallacy rarely ever applies, and factoring in the amount you had to pay to give you the opportunity you have right now is a good rule of thumb when considering whether to take the opportunity. Given that we are foolish humans, and will always make mistakes, committing the sunk cost fallacy is the right mistake to make.

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You're walking through an empty park when a tissue falls out of your pocket and blows a few metres away. You walk over to it, bend down and pick it up, and put it in a nearby garbage can. On the way you pass dozens of other pieces of trash, but leave them where they are.

Are you a proponent of the [Copenhagen interpretation of ethics](https://laneless.substack.com/p/the-copenhagen-interpretation-of-ethics)? No? Then picking up any of the pieces of trash makes the same impact on the environment, so you might as well pick up the one that's closest to you.

In fact why pick it up at all? If you think cleaning the park is a worthwhile use of your time, you should clean it whether or not you dropped the tissue. If it isn't worthwhile, why clean it just because you've dropped a tissue?

Now I agree that you are acting irrationally in this particular case. But a moral principle that you fix what you broke is a pretty good principle to have, as it discourages people from breaking things. Maybe next time you'll be more careful to stop things falling out your pockets. Whereas if you just ignored whatever mess you make as not worth your time, you'll soon become lackadaisical about your impact on the environment and start dropping trash on the floor willy nilly.

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Chesterton's fence states that you shouldn't remove a seemingly useless fence from a field until you understand why it was put there in the first place, and ascertained that it isn't actually necessary.

In the same way teaching people about all sorts of logical fallacies is dangerous if you don't make sure they understand why we make these logical fallacies in the first place. "Oh yes", the new ubermensch cries, "we should ignore our sunk costs", and then proceeds to divorce his wife of 10 years and have sex with the pretty girl he saw at the bar last night. "What's done is done", he says when his ex-wife can't make rent and his kids end up homeless, "there's no more reason for me to help you over any of the other homeless people - have 10 dollars, and don't spend it on alcohol or drugs".

Exploring logical fallacies should be done hand in hand with working out both why we make these mistakes, the exact boundaries where the fallacy truly applies, and what rules of thumb we should replace it with instead.

Now if you'll excuse me, I just remembered I dropped a tissue when I went to Jamaica on vacation last week, I'm off to pick it up.