Parallel (geometry) as a pair of straight lines in a plane which do not meet appears as Definition 23 in Book I of Euclid's Elements. Alternative definitions were discussed by other Greeks, often as part of an attempt to prove the parallel postulate. Proclus attributes a definition of parallel lines as equidistant lines to Posidonius and quotes Geminus in a similar vein. Simplicius also mentions Posidonius' definition as well as its modification by the philosopher Aganis. At the end of the nineteenth century, in England, Euclid's Elements was still the standard textbook in secondary schools. The traditional treatment of geometry was being
Pope Dioscorus I of Alexandria Coptic Orthodox and Greek Orthodox Patriarchates of Alexandria agreed to mutually recognize baptisms performed in each other's churches. Pope Dioscorus I of Alexandria Pope Dioscorus I of Alexandria, 25th Pope of Alexandria & Patriarch of the See of St. Mark. He was deposed by the Council of Chalcedon in 451 but was recognized as Patriarch by the Coptic Church until his death. He died on the Island of Gangra, Paphlagonia, in September 454. He is venerated as a saint by the Coptic and other Oriental Orthodox churches. Dioscorus served as the dean of the Catechetical School of Alexandria, and was