Euclid's Elements Euclid's Elements The Elements ( "Stoicheia") is a mathematical treatise consisting of 13 books attributed to the ancient Greek mathematician Euclid in Alexandria, Ptolemaic Egypt c. 300 BC. It is a collection of definitions, postulates, propositions (theorems and constructions), and mathematical proofs of the propositions. The books cover plane and solid Euclidean geometry, elementary number theory, and incommensurable lines. "Elements" is the oldest extant large-scale deductive treatment of mathematics. It has proven instrumental in the development of logic and modern science, and its logical rigor was not surpassed until the 19th century. Euclid's "Elements" has been referred to as the
Greek Orthodox Patriarchate of Alexandria and all Africa Greek Orthodox Patriarchate of Alexandria and all Africa The Greek Orthodox Patriarchate of Alexandria and all Africa (Greek: , "Patriarcheîon Alexandreías kaì pásēs Aphrikês") is an autocephalous Byzantine Rite jurisdiction of the Eastern Orthodox Church, having the African continent as its canonical territory. It is commonly called the "Greek" or "Eastern" Orthodox Patriarchate of Alexandria to distinguish it from the "Coptic" or "Oriental" Orthodox Patriarchate of Alexandria. Members of the Greek Orthodox Patriarchate were once known as Melkites, because they remained in communion with the Ecumenical Patriarchate of Constantinople after the schism that followed the Council of Chalcedon in 451.