Natural philosophy, as distinguished from metaphysics and mathematics, is traditionally understood to encompass a wide range of subjects which Aristotle included in the physical sciences. According to this classification, natural philosophy is the science of those beings which undergo change and are independent of human beings. This vast field of inquiry was described in Aristotelian treatises such as Physics, On the Heavens, On Generation and Corruption, Meteorology, History of Animals, On the Parts of Animals, On the Generation of Animals, On the Soul (whose Renaissance reception is not discussed in the present entry); the so-called parva naturalia (other minor writings); and some apocrypha (e.g., the Problemata), which were taught in the universities in the Middle Ages and in the Renaissance. During the Renaissance, despite the enduring centrality of the Aristotelian paradigm for the discipline, natural philosophy was enriched and expanded by a number of further approaches. By the end of the sixteenth century natural philosophy was no longer purely identified with the Aristotelian system or a standard university curriculum. At the same time, the proliferation of new contexts and ways of learning did not automatically eliminate older ones, and this fusion contributed to the birth of modern science in a period of religious and political upheaval.