First Principles Thinking means decomposing a problem down to its foundational truths - the things that must be true - and rebuilding your understanding from scratch. Instead of reasoning by analogy ("everyone does onboarding in 12 steps, so we should too"), you ignore conventions and inherited assumptions and ask what is actually required. Popularized by Elon Musk and rooted in Aristotle, it is the deliberate opposite of copying what already exists.
It works because most processes accrete over time. Steps get added, nobody removes them, and the original reason is forgotten. When you strip the system back to bedrock, you often find that half the structure was protecting an assumption that is no longer true.
For founders, the move is concrete. Take a heavy inherited process and ask what the customer actually needs before they get value. Instead of optimizing a 12-step onboarding flow, you might discover the real answer is two steps. Use it when something feels bloated but nobody questions it: break it to its irreducible parts, throw out everything that is merely convention, and redesign from what remains.
Common mistake
The biggest mistake is using "first principles" as a label for plain contrarianism - rejecting how others do things without doing the hard work of identifying the actual foundational truths you must build back up from. Tearing down is the easy half; the value comes from rigorously rebuilding.
How to use it
Three ways to put it to work.
Everyday life
Your monthly grocery bill keeps climbing past $900
Stop benchmarking against last month and strip it to the foundational truth: what does your household actually need to eat in a week, by meals, not by habit. Rebuild the list from that base and you find a third of the cart was impulse snacks and duplicate condiments. Plan seven repeatable meals from the rebuilt list and shop only that list, skipping the aisle-by-aisle wander.
Tech
Your API auth flow requires five sequential network calls
Ignore the inherited pattern that each service fetches its own token, and ask what must be true: the client needs one verified identity and a permission set before the first request. Decompose the five calls and four exist only because the original services did not trust each other, not because the user needs them. Rebuild it as a single signed token minted at login, collapsing five round-trips into one - then delete the redundant endpoints this sprint.
Small business
Your cafe opens at 6am because it always has
Question the convention instead of treating 6am as fixed, and reduce it to the real truth: you open early to capture paying customers, not to honor a schedule. Pull the till data by half-hour and the 6 to 7am block averages four coffees while staff, lights, and a baker run at a loss. Rebuild hours from actual demand - shift the open to 7am and move that labor into the proven 8 to 10am rush - and reset the door sign Monday.
Reckon · Thinking tool
First Principles Thinking
Aristotle, popularized by Elon Musk
What it is
Decompose a problem to its foundational truths and rebuild understanding from scratch, ignoring analogies and conventions.
When to use it
When inherited processes feel heavy but nobody questions them. Strip the system back to what must be true and redesign from there.
Work through it.
Print this (use the Save as PDF button up top) and fill it in on paper. Strip an inherited process back to what must actually be true and redesign it from scratch instead of optimizing what exists.
01
THE INHERITED THING: Name the process, system, or assumption you have accepted as given without questioning it.
02
THE DECOMPOSITION: Ask 'why does this step exist?' for each part until you hit bedrock. Write the foundational truths: what must be true regardless of convention.
A bedrock truth is something physics, math, or human behavior guarantees. Convention is not bedrock.
03
THE REBUILD: Starting only from the bedrock truths, design the simplest system that achieves the core goal. Ignore how it has always been done.
04
THE GAP: Compare your rebuilt version to what exists today. List every step in the current version that has no bedrock justification.
05
THE CHANGE: Pick one unjustified step to eliminate or replace this week. Write the first action.
Reckon · reckon.report · flip for the working template
Reckon · Working template
First Principles Thinking
Print double-sided. Read the how-to on the front; do the work here.