Avicenna’s philosophy

Ibn Sina wrote extensively on early Islamic philosophy, especially the subjects logic, ethics, and metaphysics, including treatises named Logic and Metaphysics. Most of his works were written in Arabic - which was the de facto scientific language of that time, and some were written in the Persian language. Of linguistic significance even to this day are a few books that he wrote in nearly pure Persian language (particularly the Danishnamah-yi "Ala", Philosophy for Ala" ad-Dawla"). Ibn Sina’s commentaries on Aristotle often corrected the philosopher, encouraging a lively debate in the spirit of ijtihad.

In the medieval Islamic world, due to Avicenna"s successful reconciliation between Aristotelianism and Neoplatonism along with Kalam, Avicennism eventually became the leading school of Islamic philosophy by the 12th century, with Avicenna becoming a central authority on philosophy.

 This was particularly the case in Paris, where Avicennism was later proscribed in 1210. Nevertheless, his psychology and theory of knowledge influenced William of Auvergne and Albertus Magnus, while his metaphysics had an impact on the thought of Thomas Aquinas.

Metaphysical doctrine

Early Islamic philosophy, imbued as it is with Islamic theology, distinguishes more clearly than Aristotelianism the difference between essence and existence. Whereas existence is the domain of the contingent and the accidental, essence endures within a being beyond the accidental. The philosophy of Ibn Sina, particularly that part relating to metaphysics, owes much to al-Farabi. The search for a truly definitive Islamic philosophy can be seen in what is left to us of his work.

Following al-Farabi"s lead, Avicenna initiated a full-fledged inquiry into the question of being, in which he distinguished between essence (Mahiat) and existence (Wujud). He argued that the fact of existence can not be inferred from or accounted for by the essence of existing things and that form and matter by themselves cannot interact and originate the movement of the universe or the progressive actualization of existing things. Existence must, therefore, be due to an agent-cause that necessitates, imparts, gives, or adds existence to an essence. To do so, the cause must be an existing thing and coexist with its effect.

Avicenna’s consideration of the essence-attributes question may be elucidated in terms of his ontological analysis of the modalities of being; namely impossibility, contingency, and necessity. Avicenna argued that the impossible being is that which cannot exist, while the contingent in itself (mumkin bi-dhatihi) has the potentiality to be or not to be without entailing a contradiction. When actualized, the contingent becomes a ‘necessary existent due to what is other than itself’ (wajib al-wujud bi-ghayrihi). Thus, contingency-in-itself is potential beingness that could eventually be actualized by an external cause other than itself. The metaphysical structures of necessity and contingency are different. Necessary being due to itself (wajib al-wujud bi-dhatihi) is true in itself, while the contingent being is ‘false in itself’ and ‘true due to something else other than itself’. The necessary is the source of its own being without borrowed existence. It is what always exists.

 The Necessary exists ‘due-to-Its-Self’, and has no quiddity/essence (mahiyya) other than existence (wujud). Furthermore, It is ‘One’ (wahid ahad) since there cannot be more than one ‘Necessary-Existent-due-to-Itself’ without differentia (fasl) to distinguish them from each other. Yet, to require differentia entails that they exist ‘due-to-themselves’ as well as ‘due to what is other than themselves’; and this is contradictory. However, if no differentia distinguishes them from each other, then there is no sense in which these ‘Existents’ are not one and the same. 

Avicenna’s logic

Avicenna discussed the topic of logic in Islamic philosophy extensively in his works, and developed his own system of logic known as "Avicenna’s logic" as an alternative to Aristotelian logic. By the 12th century, Avicenna’s logic had replaced Aristotelian logic as the dominant system of logic in the Islamic world. After the Latin translations of the 12th century, Avicenna’s logic was also influential in Europe.

Ibn Sina developed an early theory on hypothetical syllogism, which formed the basis of his early risk factor analysis. He also developed an early theory on propositional calculus, which was an area of logic not covered in the Aristotelian tradition.

Ibn Sina also contributed inventively to the development of inductive logic, being the first to describe the methods of agreement, difference and concomitant variation which are critical to inductive logic and the scientific method.

Natural philosophy

Ibn Sina and Abu Rayhan al-Biruni engaged in a written debate, with Abu Rayhan Biruni mostly criticizing Aristotelian natural philosophy and the Peripatetic school, while Avicenna and his student Ahmad ibn "Ali al-Ma"sumi respond to Biruni"s criticisms in writing. Abu Rayhan began by asking Avicenna eighteen questions, ten of which were criticisms of Aristotle"s On the Heavens.

Other links:

Who was Avicenna?

Avicenna: Short biography

Avicenna: Early life

Avicenna: Adulthood

Avicennia"s science

Avicennian psychology

Avicenna