Abu Nasr Muhammad ibn Muhammad Farabi (also known in the West as Alpharabius) (c. 872 in Farab – between 14 December, 950 and 12 January, 951 in Damascus), was a renowned scientist and philosopher of the Islamic Golden Age. He was also a cosmologist, logician, and musician. Through his commentaries and treatises, Al-Farabi became well known among medieval Muslim intellectuals as "The Second Teacher", that is, the successor to Aristotle, "The First Teacher". This volume contains the complete texts of two fo his famous treatises - Risala Al-Huruf (Book of Letters) and Tahsil Al-Saida (The Attainment of Happiness).