Аl-Farаbi, Abu Nasr (872-950) Persian Islamic neoplatonist who employed Aristotelian logic in support of his arguments for the existence of god and used Plato's Republic as the model for his own description of civil society in Principles of Citizens of the Virtuous City. Ibn Sina, Abщ'Alм al-Husayn (980-1037) Persian Islamic philosopher and physician whose Kitab Al-Shifa (Book of Healing) commented on the philosophy of Aristotle. As a leading neoplatonist, Ibn Sina emphasized the causal necessity that characterizes emanations from the divine, but supposed that human knowledge can best be achieved by mystical illumination. Neoplatonism Philosophical system developed by Plotinus and others. Nominally derived from Plato's metaphysics, neoplatonic philosophy regards the natural world as a series of emanations from the nature of god. During most of the medieval period, this system was the most influential version of Plato's thought. Aristotelianism A tradition, dating from the medieval period, concerned with promoting and defending significant portions of the philosophy of Aristotle.