A large part of the world’s population, like the followers of the Abrahamic religions, believe in an infinitely perfect omniscient, and omnipresent entity that is known by different names, such as Yehovah, God the Father, or Allah. And others, like the Hindus, believe in an impersonal universal perfect being compatible with theism. Although the popularity of theism typically brings a strong evidential force for the believers to keep following their beliefs about God, deep down, every believer knows that this commonsensical epistemic approach of following the prevalent notions are not enough in proving the existence of God. Furthermore, on some occasions, including when we as believers are challenged by atheists or agnostics, we need to justify our beliefs more technically in terms that are accessible to a wider audience.

Therefore, philosophers and theologians in the history of religions have posed their arguments in proving the existence of God. Among the many arguments posited by these scholars, ontological, cosmological, and teleological arguments constitute the major traditional arguments for the existence of God. From among these many arguments, this article will only focus on two accounts of ontological arguments.

What is an Ontological Argument?

An ontological argument refers to a set of claims that prove the existence of God a priori (i.e. without invoking any empirical premises). This type of argument is not in need of any observation or experience data. The fact that there is no need for any premise in an ontological argument makes it the strongest argument for the existence of God. Anselm’s1 ontological argument in Christian theology is considered the pioneer version of this kind which goes back to the eleventh-century A.C. However, the historical reflections show that Anselm’s argument is not the first of such argument in Abrahamic religions. Before him, al-Farabi (872-951) in his commentary on Zeno formulated a primary version of such an argument, which was later known as “proof of the sincere” (in Arabic: Burhan al-Ṣiddiqin) in Islamic philosophy.

It is interesting to note that there are more than nineteen versions of “proof of the sincere” as reported by some philosophers.2 However, most of the scholars believe that such an argument was proposed first by God Himself in some verses of the Quran including the following verse:

“We shall (continue to) show them Our evidence in the world and within their souls until it becomes clear that the Quran is the truth. Is it not sufficient for you that your Lord witness all things?”3

According to Aallameh Tabatabaei and many others, including al-Farabi himself, the last sentence of the verse considers the testimony of God to all things as a sufficient argument for the existence of God and there is no need for any empirical premises to prove God’s existence. In other words, His existence is enough in proving His existence. This may sound like a counterintuitive argument. However, the concept is like any other self-evident proposition where understanding the exact meaning of the proposition is enough to prove it.

In what follows, two major versions of the” proof of the sincere” will be presented to explain this argument. The first one was formulated by Avicenna (980 – June 1037) and the second by Mulla Sadra (c. 1571/2 – 1640).

Avicenna’s Proof of Sincere

In chapter nine of his philosophical book, al-Isharat wa al-Tanbihatin, The Book of Directives and Remarks, Avicenna explains the proof of the sincere in his intricate and difficult to understand language. He states that:

“Every existent, if you look at in itself (in essence), without looking to the other aspects (accidents), is either such that existence would be necessary for it in itself or would not. So, if [existence] is necessary, then he is God (al-Ḥaqq) in himself (by essence), the Necessary existence by itself, and he is the Self-Existent (al-Qayyūm); And if it is not necessary, it is not true to be said it is impossible by itself, after it has been presupposed to be existent. Rather, if a condition attached in respect of its essence, such as the condition of the absence of its cause, it would become impossible; or such as the condition of the presence of its cause, it would become necessary. And, if a condition is not attached in respect of its essence, neither the occurrence of a cause nor its absence, then the third thing would remain in itself (in essence), namely, contingency; (imkān) so, it is in respect of its essence, a thing which is neither necessary nor impossible. Thus, every existent is either necessary existence by itself or contingent existence by itself.”4

In these lines, Avicenna has proposed his innovative argument and called it the “proof of the sincere” (Burnhan al-Ṣiddīqīn) for the first time. He insists that this proof depends purely on conceptual analysis of “existent” without taking into consideration any specific creature or other empirical concepts. Therefore, as he claims, we face an ontological argument that relies on understanding the universal concept of the “existent.” If we elaborate on Avicenna’s ontological argument, we can find that his argument consists of the following eight sentences:

1-     There is a “existent” somewhere. The certainty of the existence of any existent is enough in this argument; at least everyone is aware of the existence of its conscious (i.e. self-consciousness).

2-     Every existent, in itself, is either such that the existence is necessary for it, in itself without considering any external factor, or not.

3-     If the existence is necessary for it in itself, then it is “self-existent” (al-mawjud bi Nafsihi/ Wājib al-wujūd)), which is God.

4-     If the existence is not necessary for it in itself, then it is contingent in respect to its essence. In another word, its existence is neither necessary nor impossible, so it is Mumkin al-wujud.

5-     Every contingent being needs an external cause for it to come to exist.

6-     This cause either regresses to a chain of contingents which is vicious circle,5

7-     Or there is a necessary existent in this chain to which all the existents go back to.

8-     Either way, the dilemma, entails to the existence of a necessary existent (al-mawjud bi Nafsihi/ Wajib al-wujud), which is God Almighty.

All the eight mentioned sentences seem solid in themselves, but whether they are able to constitute an ontological argument or not has been a matter of debate among many theologians. While some have considered the argument a pure ontological argument, others have categorized it under the cosmological argument 6 and argued that important presuppositions, like “existent,” play a role in this argument, and hence it is not considered ontological. Others brought the two together and said it is simultaneously an ontological and cosmological argument. However, since the purpose of this article is only proving the existence of God, the typology of Avicenna’s argument is not important here.

Mulla Sadra’s Proof of the Sincere

Since “existence” is a more general and self-evident concept than “existent,” and to avoid any empirical presupposition in his ontological proof, Mulla Sadra takes “existence” and not “existent” into his account of the argument. In his major book Asfar, he says:

“And it is stated that existence, as was mentioned before, is a single, simple, objective reality (ḥaqiqah ʿayniyah). The ultimate perfection for which there is nothing greater is that which does not depend on anything else, and nothing greater than it can be imagined, for all imperfect things are dependent on others, and are in need of the more complete. … Therefore, existence is either independent of others or essentially (li dhat) in need of others…existence is either a complete reality (ḥaqiqah) necessary in its ipseity (huwiyyah), or it is essentially (dhatan) in need of it [i.e. that which is necessary in itself], substantially (jawhariyyah) relying on it. According to each of these alternatives it has been proven and demonstrated that the existence of the Necessary Existent is in its ipseity [i.e. individual identity] needless of any other. This is what we intended. And know that this argument is extremely firm and strong, and its source is near to the way of the Illuminationists,7 which is based on the principle of light.”8

We see in his explanation, Mullas Sadra’s argument, is very similar to that of Avicenna. A simplified formulation of his proof is as follows:

1-     There is an objective existence.

2-     Every existence is either complete and needless of others in itself or it is incomplete.

3-     If the existence is complete and needless of others, it would be necessary in itself and independent of any other existents; which equals to God.

4-     If the existence is incomplete, then it is contingent in respect of its essence.

5-     Every contingent being needs a cause to come to exist.

6-     This cause either regresses to a chain of contingents which is a vicious circle,9

7-     Or there is a necessary existent in this chain, to which all the existents go back to

8-     Either way, the dilemma entails to the existence of a necessary existent, which is God Almighty.

Other than the proof of the sincere, there are numerous ways through which we can prove the existence of God. In Mulla Sadra and Avicenna’s views, the “proof of the sincere” is the most reliable because there is no middle term in this argument other than His existence.10 However, one does not always need to follow a philosophical path to prove God for themselves. This fact was indeed the core reason for the emergence of many types of arguments for the existence of God. It is said that a lady using a spinning wheel was asked, “how do you understand if there is a God in this universe?” She took her hand off the spinning wheel, and the wheel stopped after a few seconds. She said, “my spinning wheel stopped without me and how can the entire universe wheel continue rolling without Him?”

1. (1033–1109) an eleventh-century Christian saint, in Proslogion.
2. Mīrzā Mahdī Ashtīyānī, Glosses on Sabzivārī’s Sharḥ al-Manẓūmah. ’Abd al-Jawād Falāṭūrī (Tehran, Tehran University Publication, 1993, P. 489).
3. Quran 41:53.
4. This is a reformed translation of the passage in: Mayer, Toby, Ibn Sīnā’s Burhān al-Ṣiddīqīn  in Journal of Islamic Studies (2001), No. 12, p. 22); for the original one see, Avicenna, al-Ishārāt wa al-Tanbīhātin, ed. Sulayman Dunya (Cairo: Dar al-Ma’arif, 1957-1968, Vol. 3, P. 19).
5. Merriam-Webster, “Vicious circle originally referred to a circular argument, that is, an argument that assumes the conclusion as one of its premises.”
6.The cosmological argument is an argument that proves the exitance of God through the universal causation law. The law demands that every effect needs a cause and universe as an effect is in need of a cause that is God. For more explanation ref: Reichenbach, Bruce, “Cosmological Argument”, The Stanford Encyclopedia of Philosophy (Spring 2019 Edition), Edward N. Zalta (ed.), URL = <https://plato.stanford.edu/archives/spr2019/entries/cosmological-argument/>.
7. an Illuminationist (ishraqi) is a philosophical school in the Islamic philosophy. Ref. to Marcotte, Roxanne, “Suhrawardi”, The Stanford Encyclopedia of Philosophy (Fall 2016 Edition), Edward N. Zalta (ed.), URL = <https://plato.stanford.edu/archives/fall2016/entries/suhrawardi/>.
8. See, Muhammad Legenhausen, The Proof of the Sincere in Journal of Islamic Philosophy, (2003, Vol. 1, No. 1).
9. Merriam-Webster,“Vicious circle originally referred to a circular argument, that is, an argument that assumes the conclusion as one of its premises.”
10. Sadr al-Dīn Muḥammad Shīrāzī, al-Ḥikmat al-Mutaʿālliyyah fi al-Asfār al-Arbaʿa (Qom: Mustafavi, 1386/1966) Vol. 6, p. 12).



سَنُرِيهِمْ آيَاتِنَا فِي الْآفَاقِ وَفِي أَنْفُسِهِمْ حَتَّىٰ يَتَبَيَّنَ لَهُمْ أَنَّهُ الْحَقُّ أَوَلَمْ يَكْفِ بِرَبِّكَ أَنَّهُ عَلَىٰ كُلِّ شَيْءٍ

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