A 1667 ethical philosophical treatise by Ethiopian philosopher Zera Yacob. The philosophy is theistic in nature and came during a period when African philosophical literature was significantly oral in character. It has often been compared by scholars to Descartes' Discours de la methode (1637). Yacob wrote his treatise as an investigation of the light of reason. Yacob is most noted for this philosophy surrounding the principle of harmony.