Abu¯ Ja far Muh. ammad Na¯s. ir al-Dı¯n al-T. u¯sı¯, mathematician, astronomer, philosopher, theologian, honored with titles such as al-Muallim al-tha¯lith (the “third teacher” after Aristotle and al-Fa¯ra¯bı¯), Khwa¯ja (“distinguished” or “learned” scholar), Usta¯dh al-bashar (“teacher of humankind”), was born on February 17, 1201, in Tus near Mashhad in present-day Iran, and died in Baghdad, Iraq, on June 25, 1274. A prolific scholar, he is rightly reckoned to have been one of the most important thinkers of the thirteenth century. His early education comprised of studies in Arabic, the Qur a¯n, h. adı¯th, and in jurisprudence according to the Twelver Shı¯ ı¯ school. His father, a well-respected jurist, encouraged al-T. u¯sı¯ to educate himself more broadly in the sciences, philosophy, and other doctrinal positions, and so he journeyed to Nishapur, where he studied mathematics, the natural sciences, and the medical and philosophical works of Ibn Sı¯na¯ (Avicenna, d. 1037) under teachers who themselves had studied with the celebrated scholar Fakhr al-Dı¯n al-Ra¯zı¯ (d. 1209). Al-T. u¯sı¯ went on to study jurisprudence in Iraq, and proceeded thence to Mawsil to study with the mathematician and astronomer, Kama¯l al-Dı¯n ibn Yu¯nus (d. 1242).