This short book is a work of one of the 20th century's greatest philosophers and historians of philosophy, Etienne Gilson. The book's title, taken from the first chapter, may sound esoteric but it reflects a common-sense outlook on the world, applied in a "methodical" way. That approach, known as realism, consists in emphasizing the fact that what is real precedes our concepts about it. In contrast to realism stands idealism, which refers to the philosophical...