Seddiqin means the argument of the sincere men or truthful ones. Seddiqin refers to Those who are just only argue for the God's existence through God. In other words, in this argument, the existence of God argued through only the existence. According to Legenhausen the Seddiqin is synonym with sincere, sincere is antonym with hypocritical.The word "Seddiqin" is a sighah mubalighah in Arabic grammar which shows extra attribution.Consequently, Seddiqin means those who are extremist in faith and belief.
The Seddiqin counted as one of the lasting and permanent argument in Islamic philosophy for the existence of God.This argument also posed by most of Islamic philosophers in different explanation to justify the Necessity Being.It seems that one who first presented the argument is Avicenna. after him, many of Islamic philosophers try to show other explanation of the Seddiqin argument.
Avicenna detailed the argument for the existence of God in three books namely Al-ShifaThe Book of Healing and Al-Nejat and Al-isharat wa al-tanbihat. it seems that for the first time applied the argument of Seddiqin. According to Muhammad Legenhausen little pay attention to Avicenna's proof of sincere.Avicenna described the argument as seddiqin( Borhane seddiqin) because this argumentation applies by those who are truthful.According to Avicenna, those who are truthful persons, their argument is pure truth while there is no symbols of untruthfulness in their argumentation.In other words, Seddiqin witness to existence of God and truth just only by one argument which is the essence of Truth and God. Avicenna refers to the argument as follows:
Consider how our statements in proving the First-almighty and His unity and his acquittance from all deficiencies did not anything other than existence itself; and there is no need to consider his creatures and acts.Also they are, also, some reasons for His existence, but this kind of demonstration is a stronger one and a higher position. this means when we survey the mode of existence we consider that existence in so far as it is existence, witness to the existence of God, then it witness to other beings
Also Avicenna quotes the Holy Quran to support the argumentation:" Is it not sufficient as regards your Lord that he is witness over all things"(surah 41, verse 53).
Avicenna focuses on the view that God is a necessary being in itself. This argument is based on contingency. The claim of Avicenna is that we can establish the existence of God directly by consideration of his existence itself. in other words in the proof of sincere, Avicenna try to reach the existence of God just through an analysis of existence itself along with the supposition that God is the necessary existent. According to him, if we reflect on any things generally and consider only to its existence, then the existence is either necessary or not. If the existence is necessary then it is God-Avicenna call it (al-Wajib al-wujud) and if the existent is not necessary then it is impossible or contingent. It is not impossible because we assume that it is something therefore it must be contingent. in fact if we considering the existence of existent alone then it is either the necessary or contingent. The contingent, in respect to its existence, needed ab alio or something which brings it into existence. The preponderant itself is necessary or contingent. If it is necessary then it is God. If it is contingent then it is in need of a transcendent cause. The series of these transcendent causes themselves are finite or infinite. The finite series finally arrives to God since that the last member doesn't need to any cause and therefore itself is by definition the Necessary Existent. If the series would be infinite then series as a whole needed to its components in its existence and therefore is contingent.
Suhrawardi, founder of illuminatinism, also referred to the seddiqin. its version is important for two reasons. first that he introduce mystical ideas into the argument. secondly mulla Sadra Shirazi known himself closer to Suhrawardi rather than Avicenna. Suhrawardi has its terminology for the argument. For instance he used word the lights of light in place of God or necessary being. He used rich for necessary being and poor for contingent being. His argument in his collected works are as follows:
If immaterial light were poor in its essence, then its need would not be for a dusky dead substance, for it would not be proper that the more noble and complete should be founded on that which is not in that direction [toward nobility], and how could the dusky benefit the light? So, if the immaterial light is needy in its occurrence, then there should be for it a supporting light. Then the ordered supporting lights will not go on to an infinite regress, as you know from the proof for the necessity of an end for things ordered into collections. So, there must be an end to the supporting lights, and their accidents and barzakh [mediation] and shapes are [directed] to a light beyond which is no further light, and that is the Light of Lights, the Comprehensive Light, the Self-Subsistent Light, the Sacred Light, the most Magnificent and Lofty of Lights, and this is the Almighty Light, and this is the absolutely needless, for no other thing is beyond it
Of course the above argument depends upon the impossibility of an infinite regress but in other books he presents as argument in which there is no need to the supposition of infinite regress. This argument is as follows:
And also by another route: A thing does not require its own nonexistence, otherwise it would not occur. The Light of Lights is a unity; in itself it has no conditions. All else is subject to it. Since it has no condition and no opposite, there is nothing which can void it, so it is self-sufficient and everlasting. And the Light of Lights is not attached to any sort of shape, whether luminous or dark, and attributes are not possible for it in any aspect
This argument has closed relation with metaphor of light. According to surawardi, if we suppose that existence is contingent then if the regress of infinite be impossible, consequently there is to be a first.
Mulla Sadra explained the proof of sincere in a way that his explanation has some differentiation not only with Avicenna's version but also with Suhrevardi's .This differentiation with Avicenna differs in the argument of the existence as an existent. In other words, he begins his argument with an existent in the world until he reached to the necessary existent. Mulla Sadra also rejects Suhrawardi’s statement of the argument from contingency.
And it is stated that existence, as was mentioned before, is a single, simple, objective reality (haqiqah ‘ayniyah). There is no difference in the essences (dhat) of its individuals, but only in perfection and imperfection and in intensity and weakness, or in other matters [not related to existence itself], for example, that between the whatnesses (mahiyyah) of the same species. 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. It has become clear that the complete is prior to the imperfect, and activity is prior to potentiality. Existence is prior to nothingness. It has also been made clear that the completion of a thing is that very thing with an addition. Therefore, existence is either independent of others or essentially (li dhat) in need of others.
The First is the Necessary Existent, which is Pure Existence than which nothing is more complete, and It is unmixed with non-existence and imperfection. The second is other than this, but is Its actions and effects, which rest upon nothing but It. And, as was mentioned, the reality (haqiqah) of existence has no deficiency, and if any imperfection occurs in it, it is only due to its being an effect, and this is because the effect cannot be of an equal degree to the existence of its cause. So, if existence were not something made (maj‘ul), dominated by that which brings it into existence and brings it about (as according to what it requires), it would not be imaginable that it should have any sort of imperfections. For the reality of existence, as you know, is simple. It is unlimited, not determinate, except for pure activity and occurrence, otherwise there would be mixture in it or it would have some essence other than existence in it.