Opus number developed other catalogue-number systems; among them the "Bach-Werke-Verzeichnis" (BWV-number), and the "Köchel-Verzeichnis" (K- and KV -numbers) with which are organised the works of Johann Sebastian Bach and Wolfgang Amadeus Mozart, respectively. In the classical period, the Latin word "opus" ("work", "labour") was used to identify, list, and catalogue a work of art. By the 15th and 16th centuries, the word "opus" was used by Italian composers to denote a specific musical composition, and by German composers for collections of music. In compositional practise, numbering musical works in chronological order dates from 17th century Italy, especially Venice. In common usage, the
19th-century philosophy of complexity from mathematics, astronomy, physics, chemistry, biology, and a new discipline called "sociology", which is the study of the "dynamics and statics of society". The American philosophers Charles Sanders Peirce and William James developed the pragmatist philosophy in the late 19th century. The twilight years of the 19th century in Britain saw the rise of British idealism, a revival of interest in the works of Kant and Hegel. Transcendentalism was rooted in Immanuel Kant's transcendence and German idealism, led by Ralph Waldo Emerson and Henry David Thoreau. The main belief was in an ideal spiritual state that 'transcends' the