“evil is nothing else than absence of goodness, just as darkness also is absence of light. For goodness is the light of the mind, and, similarly, evil is the darkness of the mind. Light, therefore, being the work of the Creator and being made good (for God saw all that He made, and behold they were exceeding good produced darkness at His free-will.”
Saint John of Damascus (Also known as John Damascene and as Χρυσορρόας - Chrysorrhoas, the golden speaker, and Ἰωάννης ὁ Δαμασκηνός in Greek, يوحنا الدمشقي in Arabic, and Ioannes Damascenus in Latin) was born to a wealthy and politically connected Christian family with the surname Mansour in Damascus in 675 AD. His grandfather was Mansour ibn Sarjun, a famous member of the family who had been given the task of tax collection by the Roman Emperor Heraclius. When Syria fell to the Muslim Arabs, Damascus was able to keep it's large number of Christian civil servants and Saint John's father served under the Umayyad caliph. There is a large amount of historical evidence that the family name Mansour implies they belonged to Arab Christian tribes and the family name was very common among Syrian Christians. It is also possible however, that Saint John's grandfather was forced to take the Arabic name when Syria fell.
Saint John of Jerusalem writes that Saint John of Damascus served as an official to the Caliph's court and grew up with such heavy education that was multilingual - likely speaking Greek and Arabic with others. One legend holds that a monk by the name of Cosmas fell into the hands of Saracen pirates and was set apart from the other Christian slaves to be killed. Saint John's father overheard Cosmas saying he was a monk and interceded and was able to get the monk released and employed as Saint John's private tutor.
Saint John left Damascus to become a monk around 706 AD at the Mar Saba monastery. In one of his most famous writings the Apologetic Treatises against those Decrying the Holy Images, he attacked the Byzantine emperor and fought fiercly in defense of Holy icons. Emperor Leo III had just recently issued his first edict against the veneration of images and public exhibition and Saint John's simple writing style allowed the common people to be informed of the debate at hand.
Saint John was also one of the first known Christian critics of Islam and in his Concerning Heresy asked for proof that Mohammad had received the Quran from God (He argued that that Moses received the Torah in the presence of the Israelites), defended the Cross (at the time, Muslim scholars had accused him of idolatry for venerating the Cross) and ended the chapter with arguments that Islam could not from God as it allowed polygamy.
Below are selections of his writings that are most famously known (outside of his hymn used in the Byzantine Rite liturgy):
Apologetic Treatises against those Decrying the Holy Images
Fountain of Knowledge
Concerning Heresy (The first known homily translated into Arabic)
An Exact Exposition of the Orthodox Faith
Against the Jacobites
Against the Nestorians
Elementary Introduction into Dogmas
Letter on the Thrice-Holy Hymn
On Dragons and Ghosts
His three great Hymns or Canons are those on the Easter, Ascension and Saint Thomas's Sunday. A legendary account tells of a time when Leo III reportedly sent forged documents to the Caliph saying that John was forming a plot to attack Damascus. The Caliph had Saint John's hand cut off and hung in public view. A few days later, Saint John prayed deeply to the Theotokos before her icon asking for the restoration of his hand. The next morning, he woke to find his hand miraculously restored. He attached a silver hand to the icon in thanksgiving and named it the Tricheirousa - the icon is now located at the Helandarion monastery of the Holy Mountain.
Though his exact date of death is unknown, it is believed he died in 749 AD. In 1890, Pope Leo XIII declared him a Doctor of the Church and most Roman Catholic scholars consider him to be the last of the Church Fathers.