Cartesian Thinking

One-Line Definition

Doubt everything and accept only rigorously verified knowledge as the basis for judgment.

Core Concept

Descartes proposed “I think, therefore I am.” The core methodology: doubt everything → break down the problem → proceed from simple to complex → examine thoroughly.

What Problems It Solves

When information is incomplete, options are numerous, or risks are unclear, it helps anchor your judgment back to structured analysis rather than intuition.

More specifically, Cartesian Thinking is suited for questions like: How can we better understand the current situation? How can we make more rational judgments and actions?

When to Use

• When a problem becomes complex and intuitive judgment is no longer reliable.
• When the team disagrees on the next steps and needs a shared analytical framework.
• When you need to turn abstract judgments into concrete actions, checklists, or experiments.
• When existing approaches are losing effectiveness and you need to re-examine the underlying logic.

When NOT to Use

• The problem is simple, and direct execution matters more than analysis.
• Basic facts are missing, and you are only spinning conceptual wheels.
• Using the model merely to justify an existing conclusion rather than to help revise your judgment.

Summary

The four steps of the Cartesian method: the rule of doubt, the rule of analysis, the rule of synthesis, and the rule of enumeration.