Hammertime Day 10: Murphyjitsu

Link post

This is part 10 of 30 in the Hammertime Sequence. Click here for the intro.

Like, so pessimistic that reality actually comes out better than you expected around as often and as much as it comes out worse. It’s actually really hard to be so pessimistic that you stand a decent chance of undershooting real life.

Later in the day I will put up an open thread about the first cycle of Hammertime.

We finish up the first cycle with another post on planning. Murphyjitsu is CFAR’s method for planning which asks us to try to be so pessimistic as to undershoot real life.

Day 10: Murphyjitsu

Murphy’s Law states that anything that can go wrong will go wrong.

For our Mandarin-speaking readers, here’s a useful mnemonic: Murphy transliterates as 墨菲 (mo fei), which is homophonous to 莫非, “what if?” That’s why I think of Murphy’s Law as the What If Law.

In the course of making plans, Murphyjitsu is the practice of strengthening plans by repeatedly envisioning and defending against failure modes until you would be shocked to see it fail. Here’s the basic setup of Murphyjitsu:

  1. Make a plan.

  2. Imagine that you’ve passed the deadline and find out that the plan failed.

  3. If you’re shocked in this scenario, you’re done.

  4. Otherwise, simulate the most likely failure mode, defend against it, and repeat.

The first important sub-skill of Murphyjitsu is Inner Sim – the ability for System 1 to simulate failure modes.

Inner Sim

I have the suspicion that everyone is secretly a master at Inner Sim, the ability to instantly simulate failure. Imagine a friend declares to you their New Year’s Resolution: to write a novel, to go on a keto diet, to write a month-long sequence on instrumental rationality.

Now, listen for that internal scoffing – your System 1 instantly proliferates the future with all manner of obstacles. That’s Inner Sim at work.

If you’re anything like me, Inner Sim is better at predicting other people’s failure modes than your own. The mental move that helps apply Inner Sim introspectively is essentially Outside View: take your plan and imagine another person made them. What will go wrong?

Welp Mentality

Inner Sim does surprisingly little on its own.

I had a conversation with a rationalist friend (let’s call him “Alex”) that went something like this:

Alex: What’s bothering you?

Me: I’ve been terribly unproductive. I’m procrastinating on fellowship essays … they’re due in two weeks, and every time I think about math these essays pop up in my head.

Alex: Why?

Me: I essentially finished them, but I still have to edit it. Copy-editing is so tedious, and every run I make through my writing, it looks even more awkward than it did the previous time.

Alex: What do you predict will happen?

Me: Well … I’m going to put the essays off until two days before the deadline, edit for ten minutes when I start feeling the pressure, and submit them. Until then, I won’t get any research done.

Alex: So…?

Me (shrugs): Sucks, right?

Alex breaks down in laughter.

I call this Welp Mentality. Welp Mentality is noticing that your plans are likely to fail catastrophically, or run overtime, or take 10x as much effort as you thought, and then shrugging noncommittally. Welp.

Welp Mentality is knowing and accepting as a fact of life that every build will release two months late. That you’ll end up half-assing problem sets and essays starting midnight before the deadline. That your current exercise plan will probably peter out. I had an old motto for Welp Mentality: “Due tomorrow? Do tomorrow.”


Murphyjitsu is the astounding notion that if you can predict a failure mode, you can do something about it!

If your builds release two months late every time, you can move the release date, or cut features, or hire more engineers. If you know you’re only going to spend six hours on a problem set the night before the due date, at very least you might as well just set a six-hour Yoda Timer for it, do it at a convenient time, and submit whatever you end up with.

In my fellowship essay case, I decided to spend ten minutes editing and submit the thing immediately. The relief of getting two weeks of my life back was palpable.

Pick a plan you have for the near future. Murphyjitsu it. Pull out all the stops: Arrange social pressure to keep you on track. Double the amount of time you spend. Set calendar and phone reminders. Murphyjitsu only stops when you would be shocked if the plan fails.

Daily Challenge

Murphyjitsu a central life goal. Are there glaring failure modes you haven’t defended against?