The original source of this account of the Septuagint version is a letter purporting to have been written by Aristeas, or Aristæus, a confidential minister of Ptolemy Philadelphus, to his brother Philocrates.  Though the letter is not regarded as genuine its statements are in part admitted to be true, being confirmed by a fragment, preserved by Eusebius (Præparatio Evangelica, ix. 6.), of a work of Aristobulus, a Jewish philosopher who wrote in the reign of Ptolemy Philometor, 181–146, b.c.  Upon these testimonies it is generally admitted that “the whole Law,” i.e. the Pentateuch was translated into Greek at Alexandria in the reign either of Ptolemy Soter (323–285, b.c.), or of his son Ptolemy Philadelphus (285–247, b.c.), under the direction of Demetrius Phalereus, curator of the King’s library.