The convention in Islamic philosophy is to state that one is repeating the wisdom of the past, thus covering over such originality as may exist.There was a tendency among Islamic philosophers to cite Aristotle as an authority in order to validate their own claims and ideas.Some scholars have divided his works into those which admit Aristotelian influence, such as Kitab al-huruf (The Book of Letters), and more popular works, such as Kitab fi mabadi' ara' ahl al-madina al-fadila (The Book of the Principles of the Opinions of the People of the Virtuous City), usually known simply as al-Madina al-fadila (The Virtuous City), a utopian treatise which espouses Neoplatonic theories such as emanation, in which everything is said to flow from the One.
While aspects of Avicennan philosophy continue the Aristotelian tradition in broad terms, Ibn Sina's ideas about the Necessary Existent and the Possible Existent do not have their antecedents in Aristotle's philosophy (see Ibn Sina).
Later, transmission of these works to Christian Europe allowed Aristotelianism to flourish in the scholastic period.
We should not take at face value the Islamic philosophers' claims that they were simply following Aristotle.
However, as Ibn Sina himself hailed from Khurasan, one cannot dismiss the possible influences of Buddhism, Zoroastrianism and Hinduism on his philosophy.
The differences with Aristotle go back to the fact that the philosophers are writing in an Islamic milieu, and certain changes had to take place to correlate with the religious ideology.