The most fundamental characteristic of Ibn Sina's thought is...

The most fundamental characteristic of Ibn Sina's thought is that of arriving at definitions by a severely rigorous method of division and distinction of concepts. This lends an extraordinary subtlety to his arguments. It can often give his philosophical reasoning a strongly scholastic complexity and intricacy of structure which can annoy the modern temperament, but it is doubtlessly true that it is also this method which has resulted in almost all the original doctrines of our philosopher.

It has enabled him to formulate his most general and basic principle, viz., to every clear and distinct concept there must correspond a distinctio in re , a principle on which later Descartes also based his thesis of the mind-body dualism. The fecundity and importance of this principle of analysis in Ibn Sina's system are indeed striking: he announces it recurrently and at all levels, in his proof of the mind-body dualism, his doctrine of universals, his theory of essence and existence, etc.

Examples of this principle are: “that which is affirmed and admitted is different from that which is not affirmed and admitted,” [^2] and “a single conceptual (lit.

specific) entity cannot be both known and unknown at the same time except with regard to different aspects.”[^3] This chapter will deal mostly with those concepts and doctrines of Ibn Sina which are not only capital and bring out the nature of his system, but have also both been influential and originally elaborated by him to a greater or lesser extent. The Doctrine Of Being Ibn Sina's doctrine of Being, like those of earlier Muslim philosophers, e. g., al-Farabi, is emanationistic.

From God, the Necessary Existent, flows the first intelligence alone, since from a single, absolutely simple entity, only one thing can emanate. But the nature of the first intelligence is no longer absolutely simple since, not being necessary-by-itself, it is only possible, and its possibility has been actualized by God.

Thanks to this dual nature which henceforth pervades the entire creaturely world, the first intelligence gives rise to two entities: (i) the second intelligence by virtue of the higher aspect of its being, actuality, and (ii) the first and highest sphere by virtue of the lower aspect of its being, its natural possibility.

This dual emanatory process continues until we reach the lower and tenth intelligence which governs the sublunary world and is called by the majority of the Muslim philosophers the Angel Gabriel.