And in this First no duality can be imagined, for if a second were assumed, it must be of the same level of existence and of the same nature as the First, and they would have one nature in common in which they would participate by generic participation and would have to be distinguished through specific differences, additional to the genus, and both would be composed of genus and specific difference, and everything which is of this description is temporal;
And this is what Avicenna meant by his assertion that the necessary existent must be a necessary existent, either through its own special character or through an addition which is not peculiar to it; if through the former, there cannot be two existents which are both necessary existents; if through the latter, both existents must be composed of a universal and of a peculiar entity, and the compound is not a necessary existent through itself. And if this is true, the words of Ghazali : ‘What prevents us from representing two existents which should both be of a necessary existence?’ are absurd.
But here's where some issues exist.
Why do two realities have to be separate?
For example, if I say, there is a lake, and there is a river, and there is an ocean,
Sure, they can be separate entities, or they can be connected in various ways. Here, we aren't even taking a look at this.
If Amr is a man because he is Amr, it means in the "pool of water" which is Amr's reality, he is a man. However, what if there is a larger "pool of water" which connects Amr to mankind, but not to animalkind, in such a manner?
Blessings,if amr is a man because of a shared general nature to mankind,and there were other men with a generalized nature of mankind,he and the others would be composite(being of a generalized man nature and a specific nature that differentiates him/them from other men)he would thus be a effect,dependant,finite and limited and also temporal.
the unique necessary being,can not be composite or he is an effect of two parts,and he is dependant on those parts,and thus not unconditioned.
Multiplicity by definition means differentiation and seperation,two neccessary beings would have a specific differentiating point of subjectivity,awareness or personhood(Allaah is not a person and doesn't and cannot have quiddity but I am taking the polytheist or trinitarian view in mind here)on top of a shared general nature of 'neccessariness'or 'divinity'which is impossible and makes them all metaphysically composite effects and thus creations.Why do two realities have to be separate?
they would not be 'neccessary beings'but effects,but if Allaah is divine due to his specific nature alone,none can share in his divinity,he has one nature metaphysically(no parts),and is absolutely one and unique in his mode of being.
The Qu'raan says allah is A7ad,which in arabic means a absolute oneness and unicity,he has no physical or metaphysical parts,or even different attributes which differentiate him internally,or in his mode of being,putting those things in parts,and thus making him restricted,limited and thus finite.
'two neccessary beings'would mean as Avicenna accurately said ,interdependance,which is impossible,as it means they are composed of existance and non-existance,being of two mutually incompatible,contrary natures at the same time in the same respect,which is a contradiction logically and in the basic law of identity.
And against circular causation or mutually dependant finite beings:
Circular causation from then perspective of cause in esse { symmetric and reflexive relation must not be implied} is impossible and infinite regress in vertical or essential { given the transitive relation ] is verily impossible ontologically speaking . Otherwise in linear causal series such regress is impossible , however circular causation entails the conjuction of the contraries , as it entails that the preponderant agent and the recipient or [maqbul] actualised agent is same at the same time, that means the same ontological referent possess existence and does not possess existence at the same time [ given their essential contingency] .So such mutually exclusive predication is logically impossible as it undermines the 1st axiom of classical logic[ law of identity]
Basically,a neccessary existant is a being that is self-sufficient,not dependant on prior parts,unrestricted in it's mode of being and a causeless cause and not a effect.
all finite things we see around us,contigencies,accidental qualities are made up of parts,are temporal and have the nature of being effects.there must be a causeless cause that is not conditioned upon pther realities and is self-sufficient,or neccessary existance,of which there can be only one unique being being identical to these.
this is asserting basically square-circles.
Allah can only be divine,because of his specific nature,and thus none can share in his divinity,and he is identical to his specific nature,and thus utterly one and unique,not being made of parts or being a composite effect of two natures.
al ghani,the totally self-sufficient and independant.dependant on none but himself,the basic idea of aseity in any coherent conception of God.