(Well, actually you didn't ask; actually I asked, but it's an interesting question, and I'm sure you meant to ask it.) The way I think about it, there are 5 criteria worth considering--at least as starting points:
1. A Rule of Thumb is succinct. It usually consists of a few well-chosen words that are absolutely spot on. Not long ago, I was talking with a friend about emotions and relationships. He said to me, "The opposite of love isn't hate. It's indifference." Bam! Short. Succinct. To the point. Spot on. The words were well-chosen and perfectly placed. It was as if he'd invented an insight or an aphorism on the spot.
2. A Rule of Thumb captures something you've been fumbling around in your own head trying to figure out. Someone can say something that is succinct and to the point, but if it isn't something that you've been working on yourself (even if you don't know you're working on it) it isn't going to connect with you. But if you've been thinking about work or entrepreneurship, family or career, and then someone unexpectedly nails your quest for insight with a simple observation, it's like taking a 2 x 4 on the forehead.
3. A Rule of Thumb opens up a new line of sight for you. I call the practice of capturing Rules "mental chiropracty." You know it when it happens because all of a sudden your brain snaps into alignment.
4. A Rule of Thumb helps you make sense. It puts words to a way of seeing or thinking. It opens your eyes to something that was right there in front of you, but you hadn't had the lenses to see it yet.
5. A Rule of Thumb gets you thinking. If it doesn't make you thirst for the next logical application of that kind of insight, then it's not really a rule; it's just a good line. But when you start to think about things with a fresh mind, and it applies to a number of areas that regularly come into your work or life, then you're putting a rule of thumb to very good use.
That's it for me, in a nutshell.
What would you add?
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