The ontological argument in Islam

Islam's contribution to the ontological argument is Ibn Sina's (Avicenna, d. 1037) proof of the Necessary Existent, which predates Anselm by several decades. Ibn Sina begins from the observation that whatever exists is either necessary in itself or merely possible. A merely possible being requires a cause; if every being were merely possible, the chain of causes would have no terminus. So there must be a being whose essence just is existence — the Necessary Existent (wajib al-wujud). This is not quite Anselm's argument, but it shares the ontological argument's distinctive move of inferring existence from a concept of perfection.

Ibn Sina's proof was decisive for medieval philosophy. Translated into Latin as part of the wave of twelfth-century Arabic-to-Latin scholarship, it shaped Anselm's successors and gave Aquinas a foil. Aquinas accepted much of Ibn Sina's metaphysics while rejecting the specifically ontological form — his cosmological Five Ways are in part a Christian response to Avicennian modal metaphysics. al-Ghazali, in The Incoherence of the Philosophers, attacked Ibn Sina's deployment of it as over-reliant on Greek necessity and insufficiently attentive to Qur'anic teaching on divine will.

Modern Muslim philosophy has continued to defend and refine the argument. Mulla Sadra (d. 1640) gave it an existential reading in his transcendent philosophy (al-hikma al-muta'aliya); contemporary Iranian philosophers like Mehdi Haeri Yazdi and Seyyed Hossein Nasr have presented it to English-speaking audiences. Critics — inside and outside Islam — raise the Kantian objection against the Sadrian form and Ghazali's original objection against the Avicennian form. The argument's historical importance is undisputed; its persuasive force for contemporary audiences remains contested.