First principles
Break a problem down to what is definitely true and rebuild from there, instead of copying what everyone else does. Learn the four steps and when copying is actually the smarter choice.
First-principles thinking
Taking a problem apart until you reach things that are definitely true, then building your answer up from those, not from what others do. The test for a first principle: it would still be true if everyone around you did things differently.
'A shop needs customers who pay more than the goods cost' is a first principle. 'A shop needs a nice logo before it opens' is a custom.
Two ways to reach an answer
By analogy
What do people like me usually do? Fast, and usually good enough. It carries other people's experience for free. It also carries their mistakes, their budgets and their situation, which may not be yours.
From first principles
What am I actually trying to get, and what must be true to get it? Slow and tiring. Worth it when the decision is big, when the usual answer is too expensive for you, or when the usual answer has stopped working.
Check yourself
Omid wants to get fit. His friends all joined an expensive gym, so he is about to pay for a full year. Which thought is first-principles thinking?
- 'My friends are sensible people and they all chose the same gym, so paying for a year must be right'
- 'The most expensive gym has the best equipment, so it must give the best results'
- 'Gyms are a scam; I will run outside and never pay for exercise'
- 'What I need is regular effort I can recover from. Which setup will I actually keep up?'
Show the answer
'What I need is regular effort I can recover from. Which setup will I actually keep up?'
Yes. He went back to what fitness definitely requires, regular effort he keeps up, and only then asked which setup serves it. The answer might still be the gym.
The four steps
- Say the real goal in one plain sentence
Not 'open a candle shop' but 'earn extra income each month from making candles'.
- List everything you believe the goal requires
Write it all down without judging: website, logo, 500 candles in stock, a studio, paid ads.
- Mark each line: definitely true, or just usual?
Ask 'how do I know?' and 'would it still be true if nobody did it this way?'. Be honest about the ones you merely heard.
- Rebuild from the true lines only
Find the simplest thing that satisfies them. Add the usual extras later, one at a time, when you can see what each one buys you.
Sara's candle business: what is definitely true?
1. Someone must want the candle -> unknown, must test
2. Price must be above cost -> check:
wax 3.00 + jar 2.50 + wick and scent 1.25 + box 0.75
cost per candle = 7.50
similar candles sell for about 20
3. Buyers must be able to find and pay her -> a message and a bank transfer work
4. The candle must reach them -> hand delivery or courier
Just usual, not required on day one:
website, logo, 500 in stock, studio, paid adsSimplest test that satisfies the true lines:
make 20 candles (cost 150), offer them to people she knows and one local market.
If 20 sell at 20 each, she has 400 in, 250 over materials, and proof that line 1 is true.The numbers are only an example. The point is the order: test the lines that must be true before paying for the lines that are merely usual.
Check yourself
Reza wants to work as a freelance graphic designer. Which of his beliefs are definitely true, and which are just usual?
- Clients need to see examples of his work before they hire him
- He needs a rented office to look professional
- He must earn more than he spends on tools and taxes
- He needs the newest, most expensive laptop
- He needs business cards before he can take a client
- Clients need a way to reach him and pay him
Show the answer
Definitely true: Clients need to see examples of his work before they hire him, He must earn more than he spends on tools and taxes, Clients need a way to reach him and pay him
Just usual: He needs a rented office to look professional, He needs the newest, most expensive laptop, He needs business cards before he can take a client
Check yourself
Mina is renting her first flat and has never seen a rental contract before. The first-principles move is to ask what each clause of the standard contract is there to prevent, and drop only the ones with no good answer for her case.
Show the answer
True
True. Thinking from first principles means going back to what is actually true, not throwing away what other people already learned. A standard contract is packed with lessons from past disputes that Mina can't see yet, so she asks why a clause is there before she touches it. Doing that well needs enough knowledge to tell what is true, which is the subject of the next lesson.
A USEFUL HABIT
Ask 'how do I know that?'
The assumptions that cost you most are the ones that don't feel like assumptions. A simple habit exposes them: when you catch yourself saying 'I have to' or 'you can't', ask how you know. If the answer is 'everyone says so' or 'that's what my cousin did', you have found a custom, not a fact.
'I can't change careers at 35, it's too late.' How do I know? Who told me? What would actually have to be true for it to work: skills someone will pay for, and enough savings to cover the gap.
Check yourself
Leila's family says a 'proper' engagement party needs a hall, 200 guests and a photographer, and it would use up most of her savings. She wants to use first principles. What is her best first step?
- Find the cheapest hall that still fits 200 guests
- Cancel the party: traditions are irrational and her savings matter more than one evening
- Work out what the party is really for, then find the simplest plan that does it
- Ask three friends what they spent and take the average
Show the answer
Work out what the party is really for, then find the simplest plan that does it
Right. She starts from the purpose and rebuilds. The answer may still include a hall, but now every cost has a reason she chose.
When to bother
- Use it when the decision is big, the usual answer is out of reach, or the usual answer keeps failing.
- For small, reversible choices, copying people with experience is faster and fine.
- Before dropping a custom, find out what problem it was solving.
- You can only sort true from usual in areas you understand. Outside them, borrow someone who does.
Check yourself
- Hamid: 'Every café on this street has a printed menu with 40 items, so mine needs one too.'
- Hamid: 'Customers need to know what I sell and what it costs. A chalkboard with 8 items does that.'
What changed between the first thought and the second?
- He stopped caring what customers think
- He started from what customers need, not from what other cafés do
- He decided other café owners are wrong
- He chose the cheapest option available
Show the answer
He started from what customers need, not from what other cafés do
Yes. Same decision, different starting point: the goal, not the neighbours. The chalkboard follows from what must be true.
Lesson recap
- Reasoning by analogy copies what others do; first principles rebuilds from what is definitely true.
- Four steps: state the real goal, list what you believe it needs, mark each line true or usual, rebuild from the true lines.
- 'How do I know that?' turns hidden assumptions into visible ones.
- Customs often hold hidden knowledge, so learn why one exists before dropping it, and save this tool for big decisions.