The following is a list of notable non-Muslim authors on Islam.
Chronological by date of birth
622 to 1500
Sebeos (fl. 651), Armenian historian, documented in his History the rise of Muhammad and the early Muslim conquests. Joannis Damasceni (c. 676–749), official of the Caliph at Damascus, later a Syrian monk, Doctor of the Church, his Peri Aireseon [Concerning Heresies] [t], its chapter 100 being "Heresy of the Ishmailites" (attribution questioned). Du Huan, captured at 751 Battle of Talas, traveled in Muslim lands for ten years, his Jingxingji [Record of Travels] (c. 770) contains descriptions of Muslim life; book lost, but quoted by his uncle Du You in his Tongdian (766-801), an encyclopedia of China. Sankara (c. 788–820) of Kerala, pivotal Hindu reformer; theologian of non-duality, the Advaita Vedanta: a unity of self (atman) and the whole (Brahman); unresolved is the claim that early notions of the Sufi wahdat al-wujud [Oneness of Being] was synthesized by Sankara. Abd al-Masih ibn Ishaq al-Kindi, probably 8th/9th century Abbasid, pseudonym [Servant of the Messiah...] of an Arab Christian, author of the Risalah, a dialogue with a Muslim; later translated into Latin by Pedro de Toledo, this work Apology became very influential in Europe. Nicetas Byzantius, his 9th century polemic Anatrope tes para tou Arabos... (P.G., v.105) picks at the Qur'an chapter by chapter. Mardan-Farrukh of Iran, his late 9th century Sikand-Gumanik Vigar [Doubt-Dispelling Treatise] [t] (S.B.E., v.24) favorably compares his Zoroastrianism, especially its theodicy, with Judaism, Christianity, and Islam, whose doctrines and beliefs are discussed. Petrus Venerabilis (c. 1092–1156), Abbot of Cluny (France), while in Hispania circa 1240, inspired a group led by Robert of Ketton (England), with Herman von Carinthia (Slovenia), Pierre de Poitiers (France), and the mozarab Pedro de Toledo to translate the Qur'an into Latin, hence the Lex Mahumet pseudoprophete (1143); it circulated only in manuscript copies until 1543. Often only a tinted paraphrase, later George Sales would say it "deserves not the name of translation" because of its inaccuracy. Raimundo, Arzobispo de Toledo (r. 1125–1152) sponsored uncensored translations, at first by Domingo Gundisalvo a mozarab who rendered into Latin the Spanish translations from Arabic by the converso Juan Avendaut; later joined by European scholars, e.g., Gerardo da Cremona. From books found in al-Andalus, e.g., the pagan Aristotle (centuries earlier translated from ancient Greek into Arabic by Syrian Christians), and the Muslims Ibn Sina (Avicenna), al-Ghazali, Ibn Rushd (Averroës); such translations led to controversy & the eventual "baptism" of Aristotle by Tomas d'Aquino at the University of Paris. Mose ben Maimon (1135–1204), major Jewish theologian and talmudist who fled Al-Andalus for Morocco, then Cairo, his Dalalat al-Ha'rin [Guide of the Perplexed] (Fostat 1190) [in Arabic] [t], reconciles the Bible and the Talmud with Aristotle, discusses Al-Farabi, Ibn Sina (Avicenna), and the Muslim Kalam, especially the Mutakallimun, as well as the Mutazili; influenced by Ibn Rushd (Averroës). Marco de Toledo (fl. 1193–1216) Castile, an improved Latin translation from Arabic of the Qur'an. Francesco d'Assisi (1182–1226), Italian saint, as peaceful missionary to Muslims, preached before Al-Kamil, Kurdish Sultan of Egypt, in 1219 during the fifth crusade; his Regula non bullata (1221) [t], chapter XVI "Those who are going among the Saracens and other unbelievers" counsels not to enter disputes, but rather humility, proclaiming what will please God. Frederick II (1194–1250), Hohenstaufen Emperor, at whose court in Palermo, Sicily, translations from Arabic into Latin continued. Ibn Kammuna (c. 1215-c. 1285), Jewish scholar of Baghdad, his fair-minded though controversial Tanqih al-abhat li-l-milal al-talat [Examination of the Inquiries into the Three Faiths] (1280) [in Arabic] [t]. Alfonso X el Sabio (1221–1284), Castile, his royal Scriptorium or Escuela de Traductores continued translations from Arabic (especially Greek scientific works and Islamic) into Latin, which then became widely known in Europe; many translators were Jewish. Ramon Marti (d. c. 1286) Castilla, Dominican friar, Summa contra errores Alcoranorum (1260); Pugio fidei adversus mauros et judaeos (c. 1280); a traditional partisan, he refers to the Qur'an, Hadith, as well as al-Farabi, Ibn Sina, al-Ghazali, Ibn Rushd. Tomás d'Aquino (c. 1225–1274) Italian Dominican, Doctor of the Church ("Angelicus"), his Summa contra Gentiles (c. 1261–64) [t], includes criticism of the Aristotelianism of Ibn Rushd (Averroës); also De Unitate Intellectus Contra Averroistas (Paris 1270) [t].