Linguistically a thing “ʿaraḍa ʿalā a thing” [means] it appeared in it (al-Qāmūs al-Muḥīṭ sub ʿaraḍa). A trying event (al-ʿaraḍ) is the [object of] the worries and preoccupations man is subjected to (Tahaddhub al-Lugha sub ʿaraḍa).
Terminologically, accident is defined differently by the Ashʿaris, Muʿtazila and philosophers. For the Ashʿaris, it is the possible existent which subsists in something occupying space (al-mutaḥayyiz), and is thus contingent for its existence on a substrate within which it subsists. Its self-subsistence is not conceivable because this would be irreconcilable with its nature, namely its being particular to its substrate, with the particularity of an attribute to the object of attribution. It is not a part of the object of attribution, like the subsistence of motion and stillness in a body, and like the subsistence of a colour [in a body] according to those who hold that colours are existent qualities. Since the Muʿtazila maintain that nonexistent entities are subsistent, they can also be characterised by nonexistent subsistent attributes, which constitute accidents.
Thus, for them the accident can be separated from existence which is superadded to the quiddity. They dfined accidents as that thing were it to exist would subsist in something that occupies space. Their definition, then, is of wider predicative scope than the definition of the shaira, because it included [botht] the possible existent and the possible noexistent. The philosophers on the ther hand defined it as a quiddity if encountered in extramental particulars, exists in a mawḍūʿ substratum that is a locus that is a constitutive locus mahall muqawwim for that which inheres in it li ma halla fihi such that the two things are indistinguishable with respect to a physical pointer. Its existence, then, is its existence in its substratum.
A clarificatory point
Al-Jurjānī said “it might be imagined from this expression – that is, [the accident’s] existence constituting [exactly] its existence in its substrate – that the existence of black in itself is its existence in a body, and its subsistence therein. This, however, has no basis, for it is valid for [the accident] to exist [as it is] in itself, and for it then to come to subsist in a body. It is no secret that the possibility of the subsistence of a thing in itself is distinct from the possibility of its subsistence in something other than it (Sharḥ al-Mawāqif, 5:10).
According to the kalām theologians, accidents have two divisions. The first are those which pertain specifically to living things, and the second are those which do not. Examples of the first include knowledge, life, power and the like, as well as their contraries. [Also in this category] are the instances of awareness which the kalām theologians call perceptions. The second, that is, those which does not specifically pertain to living creatures, divides into the four generations (al-akwān al-arbaʿa) and sensible entitites. The four generations are compositeness, separation, motion and rest (see the definition [of the accident] at the beginning of the Ten Categories). Objects of sense are objects perceived with the five senses.
The philosophers divided accidents into the nine categories (see al-Maqūlāt al-ʿAshra). According to the kalām theologians, certain laws govern accidents, some of which are acknowledged by all, and other regarding which there is a difference of opinion. Two principles are agreed upon.
The first is the impossibility of an accident moving from one substrate to another. There is no difference of opinion regarding this, neither amongst the kalām theologians nor amongst the philosophers. Examining the definition of the accident according to the philosophers, that is, that its existence constitutes [exactly] its existence in its substrate, it is evident that the accident cannot become actualised without its substrate. Thus, should we admit of the possibility of an accident moving from one substrate to another, we would have to admit that it become actualised without that thing by means of which it becomes actualised, and which is constitutive of it.
The second is the impossibility of a single accident subsisting in two substrata. This is known by logical necessity, whenever the conception of the concept of an accident obtains. Proof for this result consists in [simply] pointing out its necessity.
[The principles governing accidents] regarding which there is a difference of opinion are two in number. The first is the impossibility of an accident subsisting in another accident. The majority of the kalām theologians agree that this is impossibile, although the philosophers disputed this.
The kalām theologians sought proof for this result saying that [the accident’s] subsistence in its substrate consists in its being a contingent entailment of the occupation of space, of an entity which occupies space of its own essence. Now, other than substance, nothing occupies space of its own essence, and admitting the possibility of the subsistence of an accident within another accident implies that an accident could both occupy space of its own essence, and not occupy space of its own essence [simultaneously], which is a contradiction.
[This notion] was refuted by rejecting the notion that the subsistence of an accident in substance is its contingent entailment of it in its occupation of space rather its meaning is its specifically pertaining to it in the manner that an attribute specifically pertains to the thing which it describes like the manner in which white specifically pertains to a body and there is nothing to stop an accidetn subsisting in another accident according to this [definition] that is in terms of its being an attribute of it. The philosophers deduced the permissibility of this by saying that speed and sloweness are both accidetns of motion but not of bodies.
Notice
The wellspring of this difference of opinion is the difference concerning the definition of subsistence in another thing. Those who maintained that it constitutes a contingent entailment of something occupying space rejected the possibility of the subsistence of an accident, but those who interpreted subsistence as the particularity of an attribute to the object of attribution did not [reject this possibility]. The second principle governing accidents that was differed upon was the possiblity of an accident persisting for more than two discreet moments. Ashari rejected this, as did the mainstream Ashʿaris, as well as al-Naẓẓām and al-Kaʿbī amongst the Muʿtazila. What is meant by the non-persistence of an accident for two discreet moments, is that at every moment its existence passes away and likenesses of it become renewed in the substrate wherein it inhered.
One of the proofs for the impossibility of its persistence is al-Ashʿari’s deduction that were the accident to persist for two discreet moments, it would have to persist through an attribute of “persisting” subsisting within it; this would entail the subsistence of an accident within another accident, which is invalid. Accidents, thus, cannot persist for two discreet moments. This has been objected to on the grounds that persistence is not an accident, but a perspectival entity which reducible to the negation of a nonexistence posterior to existence, and that it is thus valid for an accident to be characterised by it.
Now, if it be accepted that persistence is an existent accident, we nonetheless interpet its subsistence in another to mean its specifically pertaining to it in terms of the particularity of an attribute to the object of attribution, not as constituting the contingent entailment of something that occupies space. This subsistence is thus valid, and it is on this basis that the persistence of accidents is deemed possible (Sharḥ al-Mawaqif, 2:5, Sharḥ al-Maqāsid, 1:173, Maṭaliʿ al-Anẓār, 71, Abkār al-Afkār, 351).
