An artist extends her left arm with thumb raised to the sky.
She visually positions her thumb next the head of the model sitting a dramatic pose. She notes the distance from the top of the head to the jaw line. The thumbnail serves as an impromptu ruler.
Her eyes dash back to the page. Her left thumb joins the existing lines already drawn. The artist makes her correction.
The arm finds the extended position once more. Then back to the page.
And so the dance continues.
The thumb measures distances between the chin and the shoulders. The length of an arm. The space between the feet.
The artist uses her own body to guide the proportions of her drawing. Using the thumb is both convenient and affordable. And it has worked for artists for centuries.
The original definition for the rule of thumb refers to an approximate measure in various trades. Wikipedia tells us that the average width of thumb is about an inch.
Today we speak of the “rule of thumb” differently.
In contemporary use, it is closer to describing heuristics. The rough estimate of what might occur now than many experiments have been tried. Similar results from similar efforts.
For example, a good rule of thumb is to get to the airport 2 hours before flight time. It accounts for the latency of the lines, the process for checking bags, and the time navigating to the gate.
Will it be 2 hours every time and in every airport? No. It’s simply a guideline. It’s pragmatic.
So is looking left, right, then back to left, before crossing the street on foot.
Then there’s the five-second rule. Two heads are better than one. And saving 10% of your income. They are all rules of thumb.
But whose thumb? Whose rule?
Why is that we remain in the spell of the thumb? To accept things that others repeat because they are simple to repeat.
“Fake it, until you make it” would prove disastrous for a surgeon and his first few patients.
“Feed a cold, and starve a fever” robs the body of nutrition needed to recover from an infection.
“All debt is bad” keeps you out of college or trade school when you don’t have the tuition at hand. That choice might be sound in the short term. But it may also miss supercharging your income down the road.
This is NOT to say, avoid rules of thumb. It is to say that “conventional wisdom is sometimes more convention, than wisdom.” (Roy H. Williams)
Tim Ferris learned to automatically say “no” because it helps him. He has more opportunities than time. Those of us fresh from college with debts to pay, should say “yes” to lots of opportunities.
That’s the rub when we use other people’s thumbs. They are not proportional to what fits us every time.
So, stick out your thumb to measure what is right for you. This is how you create the reality you seek.
The Visual8 