Before you read this post, I want you to do something for me.

Find yourself a hammer. If there’s not one readily convenient, it doesn’t matter too much. Anything readily wieldable and fairly heavy will do. I have a butternut squash near me. You could use one of those. If you really don’t have anything to hand and can’t be bothered to go find one, you can just use your fist I suppose.

Now, place your left (right if you’re a lefty) hand on the table in front of you, take the hammer-like object in your other hand and bring it down really hard on the hand you’ve placed on the table.

Done? OK. Read on.

You of course didn’t do this. If you did, I’m really sorry. You should probably take that as a lesson not to trust advice without thinking about it for yourself, or maybe just a lesson that I’m a bit of a dick, but I owe you a cookie. Or a hug or something. My bad.

The rest of you, though, why didn’t you do it?

Well, because it would have hurt.

You don’t need some complicated theory of inferential reasoning to tell you that hitting your hand with a hammer hurts. You’ve got a straightforward feedback process in which your body goes “OW” when heavy things impact you at high velocity. This isn’t news.

The thing that makes making predictions about the world difficult is the quality and strength of the evidence you can gather.

We conduct complicated double blind trials around medicine because it’s really hard to gather accurate and informative evidence around drug effectiveness – effects are statistical, subtle, and prone to confounders like the placebo effect.

We do not conduct complicated double blind trials around whether it’s better to jump out of an airplane with or without a parachute, because it’s really not hard to gather accurate and informative evidence about this. People who fall from high places without a parachute tend to die. People who fall from high places with one tend not to.

Issues which affect you personally have a direct evidence gathering built into them. You generally know how you feel, and you experience the results of things directly. You also have a lot of data points, because you’re on the job being you 24/7 with no holiday time.

Issues which affect other people however are much murkier. Unless you possess secret telepathic powers, you don’t have a direct hotline into their brain and you don’t know how they’re feeling. They might tell you, but by and large people are pretty well conditioned to not do that because it makes them vulnerable and because right after you’ve hurt someone is not the time when they’re feeling most inclined to trust you. You see less of any given one of them than you do of yourself, and they’re all different and confusing.

So determining activities that harm or help yourself is relatively easy, and determining activities that harm or help other people is relatively hard. In order to do the former, some simple common sense reasoning and learning from experience is more than sufficient. In order to do the latter, you need to do a reasonable amount of careful study and control for a lot of confounders.

I’m going to let you in on a spoiler: You hurt other people. This is most likely not because you’re a bad person, it’s just a thing that happens. Sometimes you do it purely by accident. Sometimes you do it because we live in an unjust society and we all implicitly support it in one way or another. Sometimes you even do it with the best of intentions.

Most of this you don’t notice because you don’t have that direct feedback – you can’t feel what it’s like to be that other person, so you don’t get a direct experience of the consequences of your actions on them. Some of it you deliberately don’t notice because you don’t want to.

Hurting yourself though? You pretty much know when you’re doing that. It’s not that we don’t do it, and it’s not that we never lie to ourselves about the fact that we are doing it, but most of the time when we do things that hurt ourselves we do so not out of ignorance but because we’ve made a conscious decision to do something painful. This isn’t always a good idea, but it is at least one made in relatively full possession of the facts.

By and large, we don’t like pain, and we’re reasonably good at avoiding it. As a result, I think it’s fair to say that the majority of us hurt other people at least as much as we hurt ourselves.

I think it’s also fair to say we don’t generally want to be hurting other people (setting aside people who enjoy being hurt and explicitly consent to it as a special case). If that’s not the case for you then… well. I’m not really sure what to suggest.

How do we stop hurting people? Or, at least, reduce how much we are hurting people.

The first step to is to understand when you’re doing it. The second step is to be able to predict whether a set of actions will do it.

That is to say, these are the skills of gathering evidence about the world and making predictions on the basis of that.

These skills are often lumped under the heading of “rationality”, or “empiricism”.

They are useful for bettering your life, but as previously mentioned you’re already awash in a sea of evidence about what causes harm or good in your life. It’s not that these skills aren’t useful here, but you’re certainly a lot closer to the point of diminishing returns than you are in cases of scarcer evidence and more complicated situations. i.e. other people.

This gives what I regard as the moral argument in favour of rationality:

It is easy to go through life being unable to accurately predict the consequences of your actions because you’ve got a rough and ready set of heuristics that mostly keep you out of harm’s way. To some degree you’re even actively encouraged to do so – ignorance really can be bliss, and understanding the world around you and being able to predict the effect of your actions will not necessarily make your life better. It may even make your life worse (more on that in another post). The prime reason to learn this skill is not to make you understand the consequences of your actions for yourself, but to understand the consequences of your actions for other people. It is a necessary skill if you want to understand how you affect the world and how to make it a better place for other people to live in.

Importantly, it also gives what I regard as the moral caveat to rationality:

You are causing at least as much harm to other people as you are to yourself.

You are developing skills which are more useful at understanding and predicting that harm for other people than they are for yourself.

Therefore, one of the consequences of improved rationality should be that you should be learning more about how your actions affect and hurt other people and how to make their lives better than you are about how to improve your own life.

If you find this is not the case, then what you are doing is not rationality, it is merely masturbation. It may feel good, and as long as it doesn’t become an unhealthy obsession there’s certainly nothing wrong with it, but it’s not exactly very productive is it?