First, the life of Muhammad or sira which generated both the Qur'an (revelation) and hadith (his daily utterances and discourses on social and legal matters), during which philosophy was defined by acceptance or rejection of his message. Together the sira and hadith constitute the sunnah and are validated by isnah ("backing") to determine the likely truth of the report of any given saying of Muhammad. Key figures are Imam Bukhari, Imam Muslim, Trimidhi, Ibn Majah, Abu Dawud and An-Nisai. Each sifted through literally millions of hadith to accept a list of under 10,000. This work, which was not completed until the 10th century, began shortly after The Farewell Sermon in 631, after which Muhammad could not mediate disputes. After his death Abu Bakr began to collect all fragments of his sayings. In this period, Muhammad was simply authority and philosophy distinguished from his personal style only by the revelation.
Second, the dominance of kalam in which questions about the sira and hadith, as well as science and law, began to be investigated beyond the scope of Muhammad's beliefs. This period is characterized by emergence of ijtihad and the first fiqh. As the Sunnah became published and accepted, philosophy separate from Muslim theology was discouraged by a lack of participants. During this period, traditions similar to Socratic method began to evolve, but philosophy remained subordinate to religion.
Third, the rise of the Mutazilite school, which built on Greek philosophy to challenge the kalam, integrate Plato and Aristotle in particular, and expand the use of ijtihad ("independent thought") to open questions of science and society, and what we today call modern philosophy. During this period the procedural traditions of Islam were highly developed. Ijtihad had strong influences on the development of the modern scientific method, while isnah is indistinguishable in form from modern scientific citation. With these tools, the Mutazilites were able to revive Greek views, and correct them. Early Muslim medicine and Early Muslim social science in particular benefited from the Mutazilite approach, but it led to very strong reaction:
Fourth, the rise of the Asharite school put an end to philosophy as such in the Muslim world, but permitted these methods to continue to be applied to science and technology. This marked the 12th-to-14th century peak of innovation in Muslim civilization, after which lack of improvements in the basic processes and confusion with theology and law had degraded methods. During this period many remarkable achievements of engineering and social organization were made, and the ulama began to generate a fiqh based on taqlid ("blind imitation") rather than on the old ijtihad. An influential 12th-century work, "The Incoherence of the Philosophers", by Al-Ghazali, laid the groundwork to "shut the door of ijtihad" later on in the 15th-century, with the assistance of the new Ottoman Empire.
Early Muslim philosophy is considered influential in the rise of modern philosophy. Aquinas knew of at least some of the Mutazilite work and the Renaissance and the use of empirical methods were inspired at least in part by Muslim works taken in Spain in 1492. The outstanding achievements of early Muslims are: