Köchel catalogue son's earlier works; Mozart's catalogue of his own compositions (begun in February 1784 with K. 449) allows relatively precise dating of many of his later works. The catalogue included the opening bars of each piece, known as an incipit. Köchel divided the corpus into a main chronology of 626 works, and five appendices ("" in German, abbreviated to "Anh.") The appendices (Anh. I-V) included: Since Köchel published his original catalogue in 1863 (now referred to as K), the dating of Mozart's compositions has been subject to constant revision. Many more pieces have since been found, re-dated, re-attributed and re-numbered, requiring
19th-century philosophy physical and empirical and is only realized through the individual's intuition, rather than through the doctrines of established religions. "Social Darwinism" refers to theories that apply the evolutionary concept of natural selection to human society. 19th-century philosophy In the 19th century, the philosophies of the Enlightenment began to have a dramatic effect, the landmark works of philosophers such as Immanuel Kant and Jean-Jacques Rousseau influencing new generations of thinkers. In the late 18th century a movement known as Romanticism began; it validated strong emotion as an authentic not of aesthetic experience, placing new emphasis on such emotions as trepidation, horror