Except Our Own Thoughts There Is

From Part III of the Discourse on the Method (1637), in René Descartes's provisional moral code (morale par provision). While engaging in radical philosophical doubt, Descartes needed practical maxims to govern his conduct in the meantime. His third maxim was to master himself rather than the world — to change his desires and judgments rather than trying to rearrange external circumstances. This Stoic-inflected principle acknowledges the limits of human power: the only domain truly under our control is our own thinking. Epictetus had expressed the identical insight in his Enchiridion fifteen centuries earlier.