Thinking books · Knowledge & truth · René Descartes, 1637

Discourse on Method — the big ideas

A short account of how to rebuild your beliefs from a foundation you cannot doubt.

Free — no account needed to read

The big ideas

Its four rules are a general method: accept nothing you do not clearly see to be true, divide difficulties into parts, order your thinking from simplest upward, and review completely enough to be sure nothing is omitted.

Methodical doubt is a tool, not a state to live in: doubting everything temporarily to find what survives.

It is unusually readable and short for a founding text of modern philosophy, which makes it one of the few originals worth going to directly rather than through a summary.

Practise it — no need to have read it

Take a conclusion you have reached about a situation. Ask what you would still be sure of if that conclusion were wrong.

A hint: Keep going until you reach something you cannot doubt, then rebuild.

Where it shows up in real life

• Unpicking a bad analysis
• Starting over on a stuck problem
• Examining inherited assumptions

This book is old enough to be freely available in most countries.

Described in our own words with the source named — never quoted, and not a substitute for reading the book.