of the attributes' derivations, Adamson commented that "a complete consideration of Avicenna's derivation of all the attributes ... would need a book-length study". In general, Avicenna derives the attributes based on two aspects of the necessary existent: (1)its necessity, which can be shown to imply its sheer existence and a range of negations (e.g. not being caused, not being multiple), and (2)its status as a cause of other existents, which can be shown to imply a range of positive relations (e.g. knowing and powerful). Reaction Reception Present-day historian of philosophy Peter Adamson called this argument one of the most influential medieval arguments for God's existence, and Avicenna's biggest contribution to the history of philosophy. Generations of Muslim philosophers and theologians took up the proof and its conception of God as a necessary existent with approval and sometimes with modifications. The phrase wajib al-wujud (necessary existent) became widely used to refer to God, even in the works of Avicenna's staunch critics, a sign of the proof's influence. Outside the Muslim tradition, it is also "enthusiastically" received, repeated, and modified by later philosophers such as Thomas Aquinas (1225–1274) and Duns Scotus (1266–1308) of the Western Christian tradition, as well by Jewish philosophers such as Maimonides (d.1204). Adamson said that one reason for its popularity is that it matches "an underlying rationale for many people's belief in God", which he contrasted with Anselm's ontological argument, formulated a few years later, which read more like a "clever trick" than a philosophical justification of one's faith. Professor of medieval philosophy Jon McGinnis said that the argument requires only a few premises, namely, the distinction between the necessary and the contingent, that "something exists", and that a set subsists through their members (an assumption McGinnis said to be "almost true by definition"). Criticism The Islamic Andalusi philosopher Averroes or Ibn Rushd (11261198) criticized the argument on its methodology. Averroes, an avid Aristotelian, argued that God's existence has to be shown on the basis of the natural world, as Aristotle had done. According to Averroes, a proof should be based on physics, and not on metaphysical reflections as in the "Proof of the Truthful". Other Muslim philosophers such as Al-Ghazali (10581111) attacked the argument over its implications that seemed incompatible with God as known through the Islamic revelation. For example, according to Avicenna, God can have no features or relations that are contingent, so his causing of