You already understand that First Principles Thinking is about breaking down problems into their fundamental truths. But how do you systematically identify those truths? It’s one thing to know you need to find the bedrock; it’s another to know how to dig. This is where a 17th-century philosopher provides a powerful toolkit.

We're moving from simply defining first principles to adopting a rigorous mental discipline for finding them. This technique is called methodological scepticism, and its architect was René Descartes A French thinker who wanted to build a system of knowledge on foundations that were absolutely certain. He argued that to find truth, you must first be willing to doubt everything – not for the sake of being negative, but as a filter to separate assumption from fact.

Think of it like inspecting a building. You wouldn’t just glance at the paint and declare it safe. You would go into the basement, check the foundations for cracks, and test the integrity of the core structure. Descartes’ method is the intellectual equivalent. It involves systematically setting aside any belief that could possibly be false, no matter how plausible it seems. The goal is to arrive at truths so fundamental they are impossible to doubt. These are your axioms.

For Descartes, the first axiom he discovered was his own existence. He reasoned that even if all his senses were deceiving him, the very act of doubting proved that there was a 'him' doing the doubting. This became his famous principle: Cogito, ergo sum (I think, therefore I am). It was his first principle, an irreducible truth discovered by stripping away all assumptions.

In modern problem-solving, your axioms won't be so philosophical, but the method for finding them is the same. An axiom is a statement you can't break down any further. It's a foundational fact, not a conclusion or an assumption.

Consider the challenge of making electric cars affordable. For years, the prevailing assumption was that batteries were fundamentally expensive, making them the biggest cost barrier.

Using Cartesian deconstruction, you would doubt this premise. Is it irrefutably true that batteries must be expensive? This shifts the focus from the 'what' (high cost) to the 'why' (what are the constituent parts and their costs?).

The practical tool for applying this doubt is Socratic questioning This disciplined, continuous process of asking questions forces you to dismantle your own assumptions. It's not about finding a quick answer but about systematically testing the validity of every component of a problem.

Let's apply it to the battery cost problem:

This line of questioning reveals that the high cost wasn't an axiom. It was a convention built on existing manufacturing processes and supply chains. The irreducible truth was the much lower cost of the raw materials. This new, foundational understanding opened the door to innovation by reframing the problem from 'How do we afford expensive batteries?' to 'How do we assemble cheap materials into a battery efficiently?'

By doubting what 'everyone knows,' you can break down a problem into its core, unchangeable parts. Only then can you begin to build a solution from the ground up.