Of course, perfect unity did not exist among the Cathari. The different names by which they were known clearly indicate certain differences of doctrine among them. Some, like the Cathari of Alba and Desenzano, taught with the Paulicians an absolute dualism, affirming that all things created came from two principles, the one essentially good, and the other essentially bad. Two other groups, the Concorrezenses and the Bagolenses, like the ancient Gnostics, held a modified form of dualism; they pretended that the evil spirit had so marred the Creator's work, that matter had become the instrument of evil in the world. Still they agreed with the pronounced dualists in nearly all their doctrines and observances; their few theoretical differences were scarcely appreciable in practice.[1] [1] On the Catharan doctrines, cf. Dõllinger's _Beiträge_. Still, contemporary writers called them by different names. In Italy they were confounded with the orthodox Patarins and Arnaldists of Milan; which explains the frequent use of the word Patareni in the constitutions of Frederic II, and other documents. The Arnaldists or Arnoldists and the Speronistæ, were the disciples of Arnold of Brescia, and the heretical Bishop Sperone. Although the chief center of the Cathari in France was Toulouse and not Albi, they were called _Albigeois_ (Albigenses), and _Tisserands_ (Texerants), because many were weavers by trade; _Arians_, because of their denial of Christ's divinity; _Paulicians_, which was corrupted into _Poplicani, Publicani, Piphes_ and _Piples_ (Flanders); _Bulgarians_ (_Bulgari_), from their origin, which became in the mouths of the people of _Bugari, Bulgri_, and _Bugres_. In fact about 1200, nearly all the heretics of western Europe were considered Cathari. Catharism was chiefly a negative heresy; it denied the doctrines, hierarchy and worship of the Catholic Church, as well as the essential rights of the State.