Descartes - Rules For The Direction of The Mind
Philosophy from Descartes

RULE V

The method consists entirely in an orderly arrangement of the objects upon which we must turn our mental vision in order to discover some truth. And we shall be observing this method exactly if we reduce complex and obscure propositions step by step to simpler ones, and then, by retracing our steps, try to rise from intuition of all of the simplest ones to knowledge of all the rest.