Classicism is a specific genre of philosophy, expressing itself in literature, architecture, art, and music, which has Ancient Greek and Roman sources and an emphasis on society. It was particularly expressed in the Enlightenment, and the Age of Reason. Classicism first made an appearance as such during the Italian renaissance when the fall of Byzantium and rising trade with the Islamic cultures brought a flood of knowledge about, and from, the antiquity of Europe. Until that time the identification with antiquity had been seen as a continuous history of Christendom from the conversion of Roman Emperor Constantine I. Renaissance classicism introduced a host of elements into European culture, including the application of mathematics and empiricism into art, humanism, literary and depictive realism, and formalism. Importantly it also introduced Polytheism, or "paganism", and the juxtaposition of ancient and modern.