so far is that it only shows the existence of a necessary existent, and that is different from showing the existence of God as worshipped in Islam. An atheist might agree that a necessary existent exists, but it could be the universe itself, or there could be many necessary existents, none of which is God. Avicenna is aware of this limitation, and his works contain numerous arguments to show the necessary existent must have the attributes associated with God identified in Islam. For example, Avicenna gives a philosophical justification for the Islamic doctrine of tawhid (oneness of God) by showing the uniqueness and simplicity of the necessary existent. He argues that the necessary existent must be unique, using a proof by contradiction, or reductio, showing that a contradiction would follow if one supposes that there were more than one necessary existent. If one postulates two necessary existents, A and B, a simplified version of the argument considers two possibilities: if A is distinct from B as a result of something implied from necessity of existence, then B would share it, too (being a necessary existent itself), and the two are not distinct after all. If, on the other hand, the distinction resulted from something not implied by necessity of existence, then this individuating factor will be a cause for A, and this means that A has a cause and is not a necessary existent after all. Either way, the opposite proposition resulted in contradiction, which to Avicenna proves the correctness of the argument. Avicenna argued that the necessary existent must be simple (not a composite) by a similar reductio strategy. If it were a composite, its internal parts would need a feature that distinguishes each from the others. The distinguishing feature cannot be solely derived from the parts' necessity of existence, because then they would both have the same feature and not be distinct: a contradiction. But it also cannot be accidental, or requiring an outside cause, because this would contradict its necessity of existence. Avicenna derives other attributes of the necessary existent in multiple texts in order to justify its identification with God. He shows that the necessary existent must also be immaterial, intellective, powerful, generous, of pure good (khayr mahd), willful (irada), "wealthy" or "sufficient" (ghani), and self-subsistent (qayyum), among other qualities. These attributes often correspond to the epithets of God found in the Quran. In discussing some