Abū Ḥāmid Muḥammad ibn Muḥammad al-Ghazālī (/ɡæˈzɑːli/; Arabic: أبو حامد محمد بن محمد الغزالي ; c. 1058 – 19 December 1111), shortened as Al-Ghazali in Arabic or Ghazali in Persian and known as Algazelus or Algazel to the Western medieval world, was a Persian theologian, jurist, philosopher, and mystic. 
Al-Ghazali has been referred to by some historians as the single most influential Muslim after the prophet Muhammad.  Within Islamic civilization he is considered to be a Mujaddid or renewer of the faith, who, according to tradition, appears once every century to restore the faith of the community. His works were so highly acclaimed by his contemporaries that al-Ghazali was awarded the honorific title "Proof of Islam" (Hujjat al-Islam ). Others have cited his opposition to certain strands of Islamic philosophy as a detriment to Islamic scientific progress, although he argued for the separation of philosophy and science.  Besides his work that successfully changed the course of Islamic philosophy—the early Islamic Neoplatonism that developed on the grounds of Hellenistic philosophy, for example, was so successfully criticised by al-Ghazali that it never recovered—he also brought the orthodox Islam of his time in close contact with Sufism. It became increasingly possible for individuals to combine orthodox theology( kalam) and Sufism, while adherents of both camps developed a sense of mutual appreciation that made sweeping condemnation of one by the other increasingly problematic. 
The traditional date of al-Ghazali's birth, as given by Ibn al-Jawzi, is 450 AH (March 1058 – February 1059 CE), but modern scholars have raised doubts about the accuracy of Ibn al-Jawzi's information, and have posited a date of 448 AH (1056–1057 CE), on the basis of certain statements in al-Ghazali's correspondence and autobiography. :23–25 He was born in Tabaran, a town in the district of Tus, which lies within the Khorasan Province of Iran. :25
A posthumous tradition—the authenticity of which has been questioned in recent scholarship—tells that his father died in poverty and left the young al-Ghazali and his brother Ahmad to the care of a Sufi. Al-Ghazali's contemporary and first biographer, 'Abd al-Ghafir al-Farisi, records merely that al-Ghazali began to receive instruction in fiqh (Islamic jurisprudence) from Ahmad al-Radhakani, a local teacher. :26–27
He later studied under al-Juwayni, the distinguished jurist and theologian and "the most outstanding Muslim scholar of his time", :29 in Nishapur, perhaps after a period of study in Gurgan. After al-Juwayni's death in 1085, al-Ghazali departed from Nishapur and joined the court of Nizam al-Mulk, the powerful vizier of the Seljuq sultans, which was likely centered in Isfahan. After bestowing upon him the titles of "Brilliance of the Religion" and "Eminence among the Religious Leaders", Nizam al-Mulk advanced al-Ghazali in July 1091 to the "most prestigious and most challenging" professoriate at the time, in the Nizamiyya madrasa in Baghdad. :34
He underwent a spiritual crisis in 1095, and consequently abandoned his career and left Baghdad on the pretext of going on pilgrimage to Mecca. Making arrangements for his family, he disposed of his wealth and adopted an ascetic lifestyle. According to biographer, Duncan B. Macdonald, the purpose of abstaining from scholastic work was to confront the spiritual experience and more ordinary understanding of "the Word and the Traditions". After some time in Damascus and Jerusalem, with a visit to Medina and Mecca in 1096, he returned to Tus to spend the next several years in ' uzla (seclusion). This seclusion consisted in abstaining from teaching at state-sponsored institutions, though he continued to publish, to receive visitors, and to teach in the zawiya (private madrasa) and khanqah (Sufi monastery) that he had built.
Fakhr al-Mulk, grand vizier to Ahmad Sanjar, pressed al-Ghazali to return to the Nizamiyya in Nishapur; al-Ghazali reluctantly capitulated in 1106, fearing (rightly) that he and his teachings would meet with resistance and controversy. :53–4 He later returned to Tus, and declined an invitation in 1110 from the grand vizier of Muhammad I to return to Baghdad. He died on 19 December 1111. According to 'Abd al-Ghafir al-Farisi he had several daughters, but no sons. :57–59
Al-Ghazali contributed significantly to the development of a systematic view of Sufism and to its integration and acceptance in mainstream Islam. As a scholar of orthodox Islam, he belonged to the Shafi'i school of Islamic jurisprudence and to the Asharite school of theology. Al-Ghazali received many titles such as Sharaf-ul-Aʾimma (شرف الأئمة ), Zayn-ud-dīn (زين الدين ), Ḥujjat-ul-Islām (حجة الإسلام ).
He is viewed as the key member of the influential Asharite school of early Muslim philosophy and as the most important refuter of the Mutazilites. However, he chose a slightly different position in comparison with the Asharites; his beliefs and thoughts differ, in some aspects, from the orthodox Asharite school.
Al-Ghazali wrote more than 70 books on the sciences, Islamic philosophy and Sufism.
Incoherence of the Philosophers
His 11th century book titled The Incoherence of the Philosophers marks a major turn in Islamic epistemology. The encounter with skepticism led al-Ghazali to embrace a form of theological occasionalism, or the belief that all causal events and interactions are not the product of material conjunctions but rather the immediate and present Will of God.
The Incoherence also marked a turning point in Islamic philosophy in its vehement rejections of Aristotle and Plato. The book took aim at the falasifa, a loosely defined group of Islamic philosophers from the 8th through the 11th centuries (most notable among them Avicenna and Al-Farabi) who drew intellectually upon the Ancient Greeks.
In the next century, Averroes drafted a lengthy rebuttal of al-Ghazali's Incoherence entitled The Incoherence of the Incoherence; however, the epistemological course of Islamic thought had already been set. Al-Ghazali gave as an example of the illusion of independent laws of cause the fact that cotton burns when coming into contact with fire. While it might seem as though a natural law was at work, it happened each and every time only because God willed it to happen—the event was "a direct product of divine intervention as any more attention grabbing miracle". Averroes, by contrast insisted while God created the natural law, humans "could more usefully say that fire cause cotton to burn—because creation had a pattern that they could discern." 
This long-held argument has been disputed. Some argue that al-Ghazali was the first intellectual to champion the separation between several disciplines formerly classified under falsafa (an Arabic word for philosophy but one that used to include physics, mathematics and logic).  "Al-Ghazali argued that some fundamentalists, who perceive falsafa to be incompatible with religion, tend to categorically reject all views adopted by 'philosophers', including scientific facts like the lunar and solar eclipses. And when that person is later persuaded of a certain view, he tends to blindly accept all other views held by philosophers". 
The autobiography al-Ghazali wrote towards the end of his life, Deliverance From Error (المنقذ من الضلال al-munqidh min al-ḍalāl) is considered a work of major importance.  In it, al-Ghazali recounts how, once a crisis of epistemological skepticism was resolved by "a light which God Most High cast into my breast ... the key to most knowledge," :66 he studied and mastered the arguments of kalam, Islamic philosophy, and Ismailism. Though appreciating what was valid in the first two of these, at least, he determined that all three approaches were inadequate and found ultimate value only in the mystical experience and insight (the state of prophecy or nubuwwa) he attained as a result of following Sufi practices. William James, in Varieties of Religious Experience, considered the autobiography an important document for "the purely literary student who would like to become acquainted with the inwardness of religions other than the Christian" because of the scarcity of recorded personal religious confessions and autobiographical literature from this period outside the Christian tradition. :307
The Revival of Religious Sciences
Another of al-Ghazali's major works is Ihya' Ulum al-Din or Ihya'u Ulumiddin (The Revival of Religious Sciences ). It covers almost all fields of Islamic sciences: fiqh (Islamic jurisprudence), kalam (theology) and sufism.
It contains four major sections: Acts of worship (Rub' al-'ibadat), Norms of Daily Life (Rub' al-'adatat), The ways to Perdition (Rub' al-muhlikat) and The Ways to Salvation (Rub' al-munjiyat). The Ihya became the most frequently recited Islamic text after the Qur'an and the hadith. Its great achievement was to bring orthodox Sunni theology and Sufi mysticism together in a useful, comprehensive guide to every aspect of Muslim life and death. The book was well received by Islamic scholars such as Nawawi who stated that: "Were the books of Islam all to be lost, excepting only the Ihya', it would suffice to replace them all."
The Jerusalem Tract
At the insistence of his students in Jerusalem, al-Ghazali wrote a concise exposition of Islam entitled The Jerusalem Tract.  :29
Works in Persian
Al-Ghazali wrote most of his works in Arabic and few in Persian. His most important Persian work is Kīmyāyé Sa'ādat (The Alchemy of Happiness). It is al-Ghazali's own Persian version of Ihya'ul ulumuddin (The Revival of Religious Sciences) in Arabic, but a shorter work. It is one of the outstanding works of 11th-century-Persian literature. The book was published several times in Tehran by the edition of Hussain Khadev-jam, a renowned Iranian scholar. It is translated to English, Arabic, Turkish, Urdu, Azerbaijani and other languages. 
Apart from Kimya, the most celebrated of al-Ghazali's works in Persian is ' Nasīhatul Mulūk (The Counseling Kings), written most probably for Sultan Ahmad Sanjar ibn Malekshah. In the edition published by Jalāluddīn Humāyī, the book consists of two parts of which only the first can reliably be attributed to al-Ghazali. The language and the contents of some passages are similar to the Kimyaye Sa'adat. The second part differs considerably in content and style from the well-known writings of al-Ghazali. It contains the stories of pre-Islamic kings of Persia, especially those of Anoshervān. Nasihatul Muluk was early translated to Arabic under the title al-Tibr al-masbuk fi nasihat al-muluk (The Forged Sword in Counseling Kings).
Zād-e Ākherat (Provision for the hereafter) is an important Persian book of al-Ghazali but gained less scholarly attention. The greater part of it consists of the Persian translation of one of his Arabic books, Bedāyat al-Hedāya (Beginning of Guidance). It contains in addition the same contents as the Kīmyāyé Sa'ādat. The book was most probably written during the last years of his life. Its manuscripts are in Kabul (Library of the Department of Press) and in Leiden.
Pand-nāma (Book of Counsel) is another book of advice and probably attributed to Sultan Sanjar. The introduction to the book relates that Al-Ghazali wrote the book in response to a certain king who had asked him for advice. Ay farzand (O son!) is a short book of counsel that al-Ghazali wrote for one of his students. The book was early translated to Arabic entitled ayyuhal walad. Another Persian work is Hamāqāti ahli ibāhat or Raddi ebāhīyya (Condemnation of antinomians) which is his fatwa in Persian illustrated with Quranic verses and Hadiths.
Faza'ilul al-anam min rasa'ili hujjat al-Islam is the collection of letters in Persian that al-Ghazali wrote in response to the kings, ministers, jurists and some of his friends after he returned to Khorasan. The collection was gathered by one of his grandchildren after his death, under five sections/chapters. The longest letter is the response to objections raised against some of his statements in Mishkat al-Anwar (The Niche of Light) and al-Munqidh min al-dalal (Rescuer from Error). The first letter is the one which al-Ghazali wrote to Sultan Sanjar presenting his excuse for teaching in Nizamiyya of Nishapur; followed by al-Ghazali's speech in the court of Sultan Sanjar. Al-Ghazali makes an impressive speech when he was taken to the king's court in Nishapur in 1106, giving very influential counsels, asking the sultan once again for excusing him from teaching in Nizamiyya. The sultan was so impressed that he ordered al-Ghazali to write down his speech so that it will be sent to all the ulemas of Khorasan and Iraq.
Al-Ghazali had an important influence on both later Muslim philosophers and Christian medieval philosophers. Margaret Smith writes in her book Al-Ghazali: The Mystic (London 1944): "There can be no doubt that al-Ghazali’s works would be among the first to attract the attention of these European scholars" (page 220). Then she emphasizes, "The greatest of these Christian writers who was influenced by al-Ghazali was St. Thomas Aquinas (1225–1274), who made a study of the Arabic writers and admitted his indebtedness to them, having studied at the University of Naples where the influence of Arab literature and culture was predominant at the time." In addition, Aquinas' interest in Islamic studies could be attributed to the infiltration of ‘Latin Averroism’ in the 13th century, especially at the University of Paris.
Dimitri Gutas and the Stanford Encyclopedia of Philosophy consider the period between the 11th and 14th centuries to be the " Golden Age " of Arabic and Islamic philosophy, initiated by Ghazali's successful integration of logic into the Islamic seminary Madrasah curriculum.  He was the first to apply the Avicennian system of temporal modal logic to Islamic theology. 
Al-Ghazali also played a very major role in integrating Sufism with Shariah. He was also the first to present a formal description of Sufism in his works. His works also strengthened the status of Sunni Islam against other schools. The Batinite (Ismailism) had emerged in Persian territories and were gaining more and more power during al-Ghazali's period, as Nizam al-Mulk was assassinated by the members of Ismailis. Al-Ghazali strongly rejected their ideology and wrote several books on criticism of Baatinyas which significantly weakened their status.
Al-Ghazali succeeded in gaining widespread acceptance for Sufism at the expense of philosophy.  At the same time, in his refutation of philosophers he made use of their philosophical categories and thus helped to give them wider circulation. 
List of works
Al-Ghazali had mentioned the number of his works "more than 70", in one of his letters to Sultan Sanjar in the late years of his life. However, there are more than 400 books attributed to him today. Making a judgment on the number of his works and their attribution to al-Ghazali is a difficult step. Many western scholars such as William Montgomery Watt (The works attributed to Al-Ghazali ), Maurice Bouyges (Essai de chronologie des oeuvres d'Al-Ghazali) and others prepared a list of his works along with their comments on each book.
Finally, Abdel Rahman Badawi, an Egyptian scholar, prepared a comprehensive list of al-Ghazali's works under 457 titles:
- from 1 to 72: works definitely written by al-Ghazali
- from 73 to 95: works of doubtful attribution
- 96 - 127: works which are not those of al-Ghazali with most certainty
- 128 - 224: are the names of the Chapters or Sections of al-Ghazali's books that are mistakenly thought books of his
- 225 - 273: books written by other authors regarding al-Ghazali's works
- 274 - 389: books of other unknown scholars/writers regarding al-Ghazali's life and personality
- 389 - 457: the name of the manuscripts of al-Ghazali's works in different libraries of the world
The following is a short list of his major works:
- al-Munqidh min al-dalal (Rescuer from Error)
- Hujjat al-Haq (Proof of the Truth)
- al-Iqtisad fil-i`tiqad (Median in Belief)
- al-maqsad al-asna fi sharah asma' Allahu al-husna (The best means in explaining Allah's Beautiful Names)
- Jawahir al-Qur'an wa duraruh (Jewels of the Qur'an and its Pearls)
- Fayasl al-tafriqa bayn al-Islam wa-l-zandaqa (The Criterion of Distinction between Islam and Clandestine Unbelief)
- Mishkat al-Anwar (The Niche for Lights),  a commentary on the Verse of Light)
- Tafsir al-yaqut al-ta'wil
- Mizan al-'amal (Criterion of Action)
- Ihya' ulum al-din, "Revival of Religious Sciences"
- Bidayat al-hidayah (Beginning of Guidance)
- Kimiya-yi sa'ādat (The Alchemy of Happiness) [a résumé of Ihya'ul ulum, in Persian ]
- Nasihat al-muluk (Counseling Kings) [in Persian]
- al-Munqidh min al-dalal (Rescuer from Error)
- Minhaj al-'Abidin (Methodology for the Worshipers)
- Maqasid al falasifa (Aims of Philosophers) [written in the beginning of his life, in favour of philosophy and presenting the basic theories in Philosophy, mostly influenced by Avicenna's works]
- Tahafut al-Falasifa (The Incoherence of the Philosophers), [in this book he refutes the Greek Philosophy aiming at Avicenna and Al-Farabi; and of which Ibn Rushd wrote his famous refutation Tahafut al-tahafut (The Incoherence of the Incoherence)]
- Miyar al-Ilm fi fan al-Mantiq (Criterion of Knowledge in the Art of Logic)
- Mihak al-Nazar fi al-mantiq (Touchstone of Reasoning in Logic)
- al-Qistas al-mustaqim (The Correct Balance)
- Fatawy al-Ghazali (Verdicts of al-Ghazali)
- Al-wasit fi al-mathab (The medium [digest] in the Jurisprudential school)
- Kitab tahzib al-Isul (Prunning on Legal Theory)
- al-Mustasfa fi 'ilm al-isul (The Clarified in Legal Theory)
- Asas al-Qiyas (Foundation of Analogical reasoning)
Reception of his work
According to William Montgomery Watt, Al-Ghazali considered himself to be the Mujaddid (Revivier) of his age. Many, perhaps most, later Muslims concurred and according to Watt, some have even considered him to be the greatest Muslim after the Prophet Muhammad.
As an example, the Islamic scholar al-Safadi states:
|“||Muhammad ibn Muhammad ibn Muhammad ibn Ahmad, the Proof of Islam, Ornament of the Faith, Abu Hamid al-Tusi (al-Ghazali) the Shafi'ite jurist, was in his later years without rival||”|
and the jurist, al-Yafi'i stated that:
He was called The Proof of Islam and undoubtedly was worthy of the name, absolutely trustworthy (in respect of the Faith) How many an epitome (has he given) us setting forth the basic principles of religion: how much that was repetitive has he summarised, and epitomised what was lengthy. How many a simple explanation has he given us of what was hard to fathom, with brief elucidation and clear solution of knotty problems. He used moderation, being quiet but decisive in silencing an adversary, though his words were like a sharp sword-thrust in refuting a slanderer and protecting the high-road of guidance.
The Shafi'i jurist al-Subki stated that:
"If there had been a prophet after Muhammad, al-Ghazali would have been the man".
Also a widely considered Sunni scholar Al Dhahabi in wrote praise of Al Ghazali: “Al-Ghazzaali, the imaam and shaykh, the prominent scholar, Hujjat al-Islam, the wonder of his time, Zayn al-Deem Abu Haamid Muhammad ibn Muhammad ibn Muhammad ibn Ahmad al-Toosi al-Shaafa’i al-Ghazzaali, the author of many books and one possessed of utter intelligence. He studied fiqh in his own town, then he moved to Nisapur in the company of a group of students. He stayed with the Imaam al-Haramayn and gained a deep knowledge of fiqh within a short period. He became well-versed in ‘ilm al-kalaam and debate, until he became the best of debater.”
Ibn Rushd (Averroes), a rationalist, famously responded that "to say that philosophers are incoherent is itself to make an incoherent statement." Rushd's book, The Incoherence of the Incoherence, attempted to refute al-Ghazali's views, though the work was not well received in the Muslim community. 
According to Firas Alkhateeb: "When one reads Imam al-Ghazali’s works at a very superficial level, one can easily misunderstand what he is saying as anti-scientific in general. The truth, however, is that al-Ghazali’s only warning to students is to not fully accept all the beliefs and ideas of a scholar simply because of his achievements in mathematics and science. By issuing such a warning, al-Ghazali is in fact protecting the scientific enterprise for future generations by insulating it from being mixed with theoretical philosophy that could eventually dilute science itself to a field based on conjecture and reasoning alone."
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Ghazali (ca. 1058–1111) Abu Hamid Muhammad b. Muhammad al-Ghazali al-Tusi (the “Proof of Islam”) is the most renowned Sunni theologian of the Seljuq period (1038–1194).
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