The rule of 3

Date: 2022-12-20 | create | writing | systems |

I believe most concepts can and should be described via the rule of 3. My arguments are:

  • You can describe most things in 3s
  • 3 is easy to remember
  • 3 forces focus

Then we'll finish with some tips on 3s in practice.

You can describe most things in 3s

Reality is complicated and there are exceptions to every rule which should sound like the basis of a contradictory argument. But despite this complication, most domains / ideas in this reality follow a power rule - the idea that a minority of the population of a dataset leads to a majority of its impact / magnitude.

I will not be proving this power rule to you here but that is the core assumption my arguments are built off of.

If we take the power rule as true (or at least applicable in most cases) then it follows that by just focusing on the most impactful minorities we capture most of the impact / value.

IME a grouping of 3 is sufficient to summarize a majority of this value. Maybe not 100%, but a representative amount.

Thus: 3 is sufficient in most cases.

3 is easy to remember

We might consider this a dumb way to measure the usefulness of something. But I'd argue that the ability to remember something is key to that thing's long-term usefulness.

The truth is that the human mind is both wildly powerful and astonishingly limited. We can communicate with mars but we can't remember what we had for breakfast yesterday - for better or worse.

The human mind can hold somewhere between 5-9 bits of info at once depending on what study you refer to (Wikipedia).

3 is great as it neatly fits into memory with bits to spare. We could do more but not by a lot and as I've already argued more shows diminishing returns and as I'll argue next those diminishing returns may actually be negative returns.

Thus: 3 is good for humans

3 forces focus

I've already argued that 3 is sufficient to describe most things and that 3 is a sufficiently small number of things for humans to keep in their mind's eye. Here I'm going to argue that doing more than 3 may actually be negative rather than positive.

The human mind is powerful. But it's also severely limited. While we can keep [5, 9] bits of info in memory at once, it may not actually be good for us to do so.

Humans are not very good at multitasking (though we can often trick ourselves into thinking otherwise). Our mind gets bogged down with the overhead of remembering context and remembering where we left off.

So if we think about the [5, 9] bits - while you could theoretically store 4 + 5 bits of info at once, really you have some bits that are devoted to context overhead, limiting how much you can actually use for your main goal.

I often liken this to the eye of Sauron. That thing is super powerful and if it looks at something it can get shit done. But it can only look at one thing at a time so it really need to prioritize what it's looking at.

3 is a good number because not only does it force things to fit in memory it also forces us to prioritize what the most important things are so we don't waste our precious bits of info capacity on things that aren't super impactful. The more we scope creep to add bits of info that aren't highly impactful to our task, the more we risk overflowing our info capacity leading to reduced performance on the main task.

Thus: limiting to 3 forces us to focus on the most impactful things and limit unnecessary info storage which may negatively impact performance.

3s in practice

You might be wondering how this works in practice and what happens when this simple rule meets with the messy complexity of reality.

Some heuristics to think about:

  • Focus on Impact - It's possible that some domains are better suited to 4 (and in some rare cases 5). That can be okay - just pay attention to what you're trying to accomplish and think about whether the additional things are actually improving that impact (and whether the ROI looks good). If it's a good investment great - but in most cases it's probably not and if you're having trouble consider trying a different chunking / grouping strategy.
  • Ideate more than 3, cull to 3 - How do you find the 3 most impactful things? Usually through experimentation. You actually have to know something decently well in order to make a good simplification like this. The good part is this should come with experience in that domain. Your knowledge of a domain is ever changing so ideate all the things you've got then just take the top 3 to start.
  • Small composable chunks > large monoliths - Even after all of these, it's likely that reality is just more complex than 3s. Right but just because everything you write about is really about life that doesn't mean everything you write has to encompass every part of life. Because you'd never finish it or do it justice. So we take the same tradeoffs here - focus on small, impactful chunks and link them together rather than trying the impossible task of encyclopedia-of-everything.

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