The affirmation or negation of existence for a particular essence is propositional. It is therefore subject to the three categories of rational judgement. Existence for an essence is as such, either necessary, impossible, or possible.
Necessary Essence: an essence whose existence does not accept negation in of itself, since its non-existence would entail absurdity. It therefore must exist, and cannot not-exist. The only necessary essence is God.
Impossible Essence: an essence whose existence does not accept affirmation in of itself, since its existence would entail absurdity. It therefore must not-exist, and cannot exist. For example: a seven-faced cube.
Possible Essence: an essence whose existence accepts both affirmation and negation in of itself, since neither its existence nor its non-existence entails any absurdity. For example: Zayd.
A possible essence accepts both of existence and non-existence in of itself. Its existence is therefore not intrinsic to it. Necessarily then, if this essence exists, this means it acquired this existence from some extrinsic being that preferred existence over non-existence for it. For this reason, existent possible essences are called contingent essences.
The extrinsic being that prefers existence over non-existence for a contingent essence, is called the specifier (Murajih). The contingent essence’s existence being preferred over its non-existence, is called a specification (Rujhan).
Notice that the non-existence of a possible essence does not require a specifier. Since a non-existent essence is not something that is real, so there is nothing to be specified. Rather, the lack of specifying (Tarjih) is the cause for the non-existence of a possible essence.
Given that contingent essences are brought into existence by an extrinsic specifier, this means that they are emergent. “Emergent” meaning: their existence is preceded by their non-existence. In other words, they began to exist.
If contingent essences were beginningless then they could not have been brought into existence (it makes no sense to “bring” into existence something that already exists). And since contingent essences were brought into existence by an extrinsic specifier, this means that they are not beginningless (i.e. emergent).
If an essence exists, then its existence is either necessary or contingent.
This is because the existence of any essence is either necessary, impossible, or possible. If impossible, then this essence cannot exist by definition. Therefore, anything that actually exists, is either necessary or contingent.
If an essence exists, then either it exists without subsisting within another essence, or it exists while subsisting within another essence.
An existent which does not subsist within another is called a being (Dhat). For example: a horse, which is a body that exists without subsisting within some other existent.
An existent which subsists within another, is called a quality (Sifa). For example: the motion of this horse, which cannot exist except by subsisting within it.
 If existence were intrinsic to the possible essence, then this possible essence wouldn’t be a possible. It would be necessary.
 The existence of a possible essence is not intrinsic to it. Therefore, either its existence is by virtue of nothing, or by virtue of an extrinsic existent. It cannot be by virtue of nothing, because “nothing” is the lack of everything, including the lack of ability to bring into existence. Thus, it is by virtue of an extrinsic existent.
 Given what was already established, the existence of a specification without the existence of a specifier, is absurd.