jml's notebook

Deciding who goes to church

I thought it would be interesting to write up how we decided who goes to church today. Even though it is such an ordinary, low-stakes event, I think it sheds light on how decisions and groups work.

I woke up this morning after a rough night of sleep. I currently have a condition that makes it difficult for me to sleep through the night. During my many wakeful periods, I had noticed that one of my children, call them K1, was coughing all the time.

I decided to myself that they should not go to church. Even if they were feeling well enough, it would be irresponsible to risk spreading the illness further.

My partner, call them B, was also not feeling great yesterday. I guessed that she'd be the one to stay home with K1. I wanted to go to church and was feeling well enough, so the only remaining question in my mind was whether our second child, K2, should come with me or stay home. I thought he should come with me, although I wanted some time alone, B & K1 would have a more restful time if K2 were out. Also, church is good for K2, and I'm more than capable of taking him there.

I formed this plan in my head, but of course that's not how group decisions work. A group decision only works if everyone has the same understanding1 of what to do2, and everyone knows that everyone has the same understanding3 of what to do. Sometimes this can be "Do what the boss says", but that's not how things work in our house. Instead, we have a conversation:

Me: I don't think K1 should go to church today

B: Yeah, you're right. That means one of us will need to stay home, though.

I know this. She knows I know this. But now we both know that we both know.

Me: Okay. How about you stay here with K1 and I'll take K2 to church.

B: Are you sure?

Me: Yeah. I'd really like to go, and you and K1 will rest better without K2 here.

B: Okay

And so everything worked out okay. No worries, no drama, just boring functional communication.

But on the way to church, I thought that this isn't rational decision making. Or perhaps better to say it's not a systematic approach to decision making. We didn't consider all the options or trade them off against the other. What are all the options? Well, we could represent this as a truth table where I'm A, B is my partner, and the kids are K1 and K2. Staying home is F and going to church is T.


That's 16 options. If you were forced to map my mental approach to the truth table, it would be something like:

  1. Set K1 = F, because K1 has to stay at home
  2. Set B = F, because I think she should stay at home
  3. Set A = T, because I want to go
  4. Look at what's left and make an actual decision.

Internally, it felt more like a branching tree than a truth table.

But we can lean on this truth table thing a bit longer.

You see, we can't leave the kids at home unsupervised, and we can't send them to church unsupervised either, and we don't want to send sick people to church. So there are three things we want to avoid:

home_alone     = not (K1 and K2) and (A and B)
church_alone   = (K1 or K2) and not (A or B)
sick_at_church = B or K1

Putting these onto the truth table looks like:

ABK1K2not home alonenot church alonenot sick at churchOK?

Honestly, just looking at this is exhausting. Extracting the gunk, we get three valid choices:

This is not how I normally make decisions.

So what's the point of all this?

One version of this story is that I had a minor problem, did the first thing that came into my head, and it worked out okay.

Another version of this story is that even making simple decisions among people who are strongly aligned in terms of values (church good; spreading disease bad; rest while sick good; unsupervised kids bad) involves establishing consensus and at minimum acknowledging choices not taken.

Or we could look at this and say that even for easy decisions, it takes quite a bit of effort to break them down into their component subdecisions and to articulate the relations between them. Perhaps this is a thing to do sparingly, or perhaps it is a trainable skill to be drilled to the point of mastery.

I don't think I've ever seen someone explicitly present a decision table in my professional career, although some design docs have had tables that come close. I have certainly been involved in woolly discussions that go around and around without resolutions. Perhaps these would have gone better if someone had constructed a decision table.

Anyway, K2 & I had a great time at church, and K1 & B had a lovely quiet morning. That's probably enough.

See also Cost of decisions and Decisions.

P.S. By the time I got to writing this, I was being tickled by memories of reading some tech luminary advocating the use of "decisions tables" in documenting designs or system architecture or something like that. Thanks to Justin Blank who both first recommended Hillel Wayne's post Decision Table Patterns to me and helped me remember that he had done so. No promises, but I might follow up by applying that post to this decision, as an exercise.


This is consensus. Not deciding a path together, but establishing that this is the path we've decided on.


I was going to say "agrees on what to do" instead of "understands what to do", but it's okay if people don't agree. They don't have to believe the decision is the best decision, they just have to agree to comply with it.


This is "common knowledge". I used to have a couple of great links for this but lost them.