JOHN CLIMACUS, abbot, ascetic, St. (ca. 579–649). John Climacus (or Joh n of Sinai, Joh n of Raithu) was abbot of the monastery of St. Catherine on Mt. Sinai during the early 7th c. His fame comes from his book, the Ladder of Paradise, from which he was graced with his surname, Klimakos, i.e., “of the ladder.” This work swiftly became and has remained ever since a classic expression of Byzantine Orthodox spirituality. It is a kind of summa or gathering together of the wisdom of previous generations of monks, though Evagrius of Pontus (q.v.) is unquestionably of the first importance among John’s sources. The Ladder continues to be required reading during Lent (q.v.) for Orthodox monastics. He is venerated in the Orthodox Church on the fourth Sunday of Lent.