The Salt Merchant’s Son
In a market town centuries ago, a boy named Tomas inherited his father’s salt stall. The salt sold for a copper coin per measure. It always had.
One morning Tomas asked his father: “Why a copper a measure?”
His father shrugged. “That’s the price.”
“But who set it?”
“The market.”
Tomas noticed something then that would shape the rest of his life. His father had answered the question without answering it. “The market” was a word doing the work of an explanation. It pointed at the question and called itself the answer. Most of what people believed, Tomas began to suspect, was held in place by words like this. Sturdy-sounding nouns guarding empty rooms.
So he walked to the coast.
He watched salt being raked from evaporation pans. He counted the hours. He weighed the labor. He measured the distance from sea to town and rented a donkey to learn what carrying cost. He sat with a tax collector over wine and learned what the road levies took. He wrote each number on a slate.
When he added them up, a measure of salt cost him, all in, a third of a copper to deliver.
But the deeper thing he noticed was this: every merchant on his road believed the price was a fact about salt. It was not. It was a fact about habit. Salt didn’t know what it cost. The sea didn’t. The donkey didn’t. The price lived nowhere except in the agreement between people who had stopped asking.
This is the first thing first principles teaches you, and it’s the part most people skip. Before you can rebuild a thing from its pieces, you have to see that it was built. Prices, job titles, org charts, the way meetings are run, what counts as a career, what counts as a good life. None of these are laws of nature. They are sediment. Someone, somewhere, made a choice, and then everyone after them inherited it as ground.
The method has three moves.
Strip the assumption. Find the sentence that starts with “everyone knows” or “obviously” or “that’s just how it works.” That sentence is a door pretending to be a wall. Reasoning by analogy stops here. Reasoning from first principles begins.
Decompose to what would survive a fire. Burn the conventions, the industry norms, the way your competitors do it. What’s left? Atoms, dollars, hours, human nature, the laws of supply and attention. Things that would still be true if every expert in your field forgot their training tomorrow. These are your pieces.
Rebuild, and notice the gap. Ask what the answer should be given only those pieces. Compare to the answer everyone has agreed on. The gap is the whole game. Sometimes the gap means the convention is wise and you’ve missed something, and you’ve just learned why the world is the way it is. Sometimes the gap is an opportunity nobody else can see, because they never looked. Either outcome makes you smarter. Most people avoid the exercise because they’re afraid of looking foolish in front of the convention. The convention does not return the favor.
Tomas undercut every salt merchant on his road, then bought their stalls when they failed. He grew old and wealthy. Near the end, his sons asked him the secret. He said: I asked why, and I didn’t accept a word for an answer.
They nodded politely. They went on charging whatever the market charged. And this, too, is part of the lesson. First principles thinking isn’t rare because it’s hard. The arithmetic Tomas did was simple. It’s rare because it requires a small, unglamorous kind of courage: to sit alone with a question your whole town has agreed not to ask