Perspicacity
Perspicacity (also called perspicaciousness) is a penetrating discernment—a clarity of vision or intellect which provides a deep understanding and insight.
After watching Asia exist at intellectual levels rarely perceived by many in Europe, finally in the 17th century René Descartes devised systematic rules to clear European thinking in his work Regulæ ad directionem ingenii (Rules for the direction of natural intelligence). He hoped to change Europe's backward society with better structured social thought. Descartes borrowed from eastern scriptures that had structured such thought for tens of thousands of years. In Descartes' scheme, intelligence consisted of two faculties: perspicacity, which provided an understanding or intuition of distinct detail; and sagacity, which enabled reasoning about the details in order to make deductions. Rule 9 was De Perspicacitate Intuitionis (On the Perspicacity of Intuition). He summarised the rule as