Ptolemy or optical factors and those caused by judgmental factors. He offered an obscure explanation of the sun or moon illusion (the enlarged apparent size on the horizon) based on the difficulty of looking upwards. There are several characters or items named after Ptolemy, including: [[File:Ptolemaeus - Quadripartitum, 1622 - 4658973.tif|thumb|"Quadripartitum", 1622]] [[Category:Ptolemy| ]] [[Category:100 births]] [[Category:170 deaths]] [[Category:1st-century Romans]] [[Category:2nd-century Romans]] [[Category:2nd-century philosophers]] [[Category:2nd-century poets]] [[Category:Egyptian calendar]] [[Category:Ancient Greek astrologers]] [[Category:Ancient Greek astronomers]] [[Category:Ancient Greek mathematicians]] [[Category:Ancient Greek music theorists]] [[Category:Astrological writers]] [[Category:Claudii]] [[Category:Egyptian astronomers]] [[Category:Egyptian mathematicians]] [[Category:Epigrammatists of the Greek Anthology]] [[Category:2nd-century people of Roman Egypt]] [[Category:Ancient Greek geographers]]
Ptolemy (gnostic) Ptolemy (gnostic) Ptolemy the Gnostic, or Ptolemaeus Gnosticus, was a disciple of the Gnostic teacher Valentinius and is known for the Letter to Flora, an epistle he wrote to a wealthy woman named Flora, herself not a gnostic. Ptolemy was probably still alive "c". 180. No other certain details are known about his life; Harnack's suggestion that he was identical with the Ptolemy spoken of by St. Justin is as yet unproved. It is not known when Ptolemy became a disciple of Valentinius, but Valentinius was active in the Egyptian city of Alexandria and in Rome. Ptolemy was, with Heracleon,