The As̱ẖ‘arite denial of Aristotle’s Prima Materia, and their views concerning the nature of space, time and causation, awakened that irrepressible spirit of controversy which, for centuries, divided the camp of Muhammedan thinkers, and eventually exhausted its vigor in the merely verbal subtleties of schools. The publication of Najim al Dīn Al‑Kātibī’s (a follower of Aristotle whose disciples were called Philosophers as distinguished from scholastic theologians) Hikmat al‑’Ain‑ ‘‘ Philosophy of Essence’‘, greatly intensified the intellectual conflict, and invoked keen criticism from a host of As̱ẖ‘arite as well as other idealist thinkers. I shall consider in order the principal points on which the two schools differed from each other.
A. The Nature of the Essence
We have seen that the As̱ẖ‘arite theory of knowledge drove them to hold that individual essences of various things are quite different from each other, and are determined in each case by the ultimate cause‑God. They denied the existence of an ever‑changing primary stuff common to all things, and maintained against the Rationalists that existence constitutes the very being of the essence. To them, therefore, essence and existence are identical. They argued that the Judgement, ‘‘Man is animal’’, is possible only on the ground of a fundamental difference between the subject and the predicate; since their identity would make the Judgement nugatory, and complete difference would make the predication false. It is, therefore, necessary to postulate an external cause to determine the various forms of existence. Their opponents, however, admit the determination or limitation of existence, but they maintain that all the various forms of existence, in so far as their essence is concerned, are identical being limitations of one Primary substance. The followers of Aristotle met the difficulty suggested by the possibility of synthetic predication, by advocating the possibility of compound essence. Such a judgement as ‘‘Man is animal’’, they maintained, is true; because man is an essence composed of two essences, animality and humanity. This, retorted the As̱ẖ‘arite, cannot stand criticism. if you say that the essence of man and animal is the same. you in other words hold that the essence of the whole is the same as that of the part. But this proposition is absurd; since if the essence of the compound is the same as that of its constituents, the compound will have to be regarded as one being having two essences or existences.
It is obvious that the whole controversy turns on the question whether existence is a mere idea or something objectively real. When we say that a certain thing exists, do we mean that it exists only in relation to us (As̱ẖ‘arite position,); or that it is an essence existing quite independently of us (Realist position)? We shall briefly indicate the arguments of either side. The Realist argued as follows:
(1) The conception of my existence is something immediate or intuitive. The thought ‘‘I exist’‘ is a ‘‘concept’’, and my body being an element of this ‘‘concept’’, it follows that my body intuitively known as something real. If the knowledge of the existent is not immediate, the fact of its perception would require a process of thought which, as we know, it does not. The As̱ẖ‘arite Al‑Rāzī admits that the concept of existence is immediate but he regards the judgement‑‘‘The concept of existence is immediate’‘ ‑ as merely a matter of acquisition. Muhammad Ibn Mubārak Bukhārī on the other hand, says that the whole argument of the realist proceeds on the assumption that the concept of my existence is something immediate ‑ a position which can be controverted. If, says he, we admit that the concept of my existence is immediate, abstract existence cannot be regarded as a constitutive element of this conception. And if the realist maintains that the perception of a particular object is immediate, we admit the truth of what he says; but it would not follow, as he is anxious to establish, that the so‑called underlying essence is immediately known as objectively real. The realist argument, moreover, demands that the mind ought not to be able to conceive the predication of qualities tothings. We cannot conceive, ‘‘snow is white’‘, because whiteness, being a part of this immediate judgement, must also be immediately known without any predication. Mulla Muhammad Ḥās̱ẖim. Husainī remarks that this reasoning is erroneous. The mind in the act of predicating whiteness of snow is working on a purely ideal existence‑the quality of whiteness ‑ and not on an objectively real essence of which the qualities are mere facets or aspects. Husainī, moreover, anticipates Hamilton, and differs from other realist in holding that the so‑called unknownable essence of the object is also immediately known. The object, he says, is immediately perceived as one. We do not successively perceive the various aspects of what happens to be the objects of our perception.
(2) The idealist, says the realist, reduces all quality to mere subjective relations. His argument leads him to deny the underlying essence of things, and to look upon them as entirely heterogeneous collections of qualities, the essence of which consists merely in the phenomenal fact of their perception. in spite of his belief in the complete heterogeneity of things, he applies the word existence to all things a tacit admission that there is some essence common to all the various forms of existence. Abul ‑ Ḥasan al‑As̱ẖ’arī replies that this application is only a verbal convenience, and is not meant to indicate the so‑called internal homogeneity of things. But the universal application of the word existence by the idealists, must mean, according to the realist, that the existence of a thing either constitutes its very essence, or it is something superadded to the underlying essence of the thing. The first supposition is a virtual admission as to the homogeneity of things since we cannot maintain that existence peculiar to one thing is fundamentally different from existence peculiar to another. The supposition that existence is something superadded to the essence of a thing leads to an absurdity; since in this case the essence will have to be regarded as something distinct from existence and the denial of essence (with the As̱ẖ‘arite) would blot out the distinction between existence and non‑existence. Moreover, what was the essence before existence was superadded to it ? We must not say that the essence was ready to receive existence before it actually did receive it since this statement would imply that the essence was non‑existence before it received existence. Likewise the statement that the essence has the power of receiving the quality of non‑existence, implies the absurdity that it does already exist, Existence, there‑fore, must be regarded as forming a part of the essence. But if it forms a part of the essence, the latter will have to be regarded as a compound. If, on the other hand, existence is external to the essence, it must be something contingent because of its dependence on something other than itself. Now everything contingent must have a cause. If this cause is the essence itself, it would follow that the essence existed before it existed since the cause must precede the effect in the fact of existence. If, however, the cause of existence is something other than the essence, it follows that the existence of God also must be explained by some cause other than the essence of God‑an absurd conclusion which turns the necessary into the contingent. This argument of the realist is based on a complete misunderstanding of the idealist position. He does not see that the idealist never regarded the fact of existence as something superadded to the essence of a thing; but always held it to be identical with the essence. The essence, says Ibn Mubārak, is the cause of existence without being chronologically before it. The existence of the essence constitutes its very being; it is not dependent for it on something other than itself,
The truth is that both sides are far from a true theory of knowledge. The agnostic realist who holds that behind the phenomenal qualities of a thing, there is an essence operating as their cause, is guilty of a glaring contradiction. He holds that underlying the thing there is an unknowable essence or substratum which is known to exist. The As̱ẖ‘arite idealist, on the other hand, misunderstands the process of knowledge. He ignores the mental activity involved in the act of knowledge; and looks upon perceptions as mere presentations which are determined, as he says, by God. But if the order of presentations requires a cause to account for it, why should not that cause be sought in the original constitution of matter as Locke did ? Moreover, the theory that knowledge is a mere passive perception or awareness of what is presented, leads to certain inadmissible conclusions which the As̱ẖ‘arite never thought of:
(a) They did not see that their purely subjective conception. of knowledge swept away all possibility of error. If the existence of a thing is merely the fact of its being presented, there is no reason why it should be cognised as different from what it actually is.
(b) They did notsee that on their theory of knowledge, our fellow‑beings, like other elements of the physical order, would have no higher reality than mere states of my consciousness.
(c) If knowledge is a mere receptivity of pre‑seiltations, God, who, as cause of presentations, is active in regard to the act of our knowledge, must not be aware of our presentations. From the As̱ẖ‘arite point of view this conclusion is fatal to their whole position. They cannot say that presentations, on their ceasing. to be my presentations, continue to be presentations to God’s consciousness.
Another question connected with the nature of the essence is, whether it is caused or uncaused The followers of Aristotle, or philosophers as they are generally called by their opponents, hold that the underlying essence of things is uncaused. The As̱ẖ‘arite hold the opposite view. Essence, says the Aristotelian, cannot be acted upon by any external agent Al‑Kātibī argues that if, for instance, the essence of humanity had resulted from the operation of an external activity, doubt as to its being the real essence of humanity would have been possible. As a matter of fact we never entertain such a doubt; it follows therefore, that the essence is not due to the activity of an agency external to itself. The idealist starts with the realist distinction of essence and existence, and argues that the realist line of argument would lead to the absurd proposition‑ that man is uncaused; since he must be regarded, according to the realist, as a combination of two uncaused essencesexistence and humanity.
B. The Nature of Knowledge
The followers of Aristotle, true to their position as to the independent objective reality of the essence, define knowledge as ‘‘receiving images of external things’’. It is possible to conceive, they argue, an object which is externally unreal, and to which other qualities can be attributed. But when we attribute to it the quality of existence, actual existence is necessitated; since the affirmation of the quality of a thing is a part of the affirmation of that thing. If, therefore, the predication of existence does not necessitate actual objective existence of the thing, we are driven to deny externally altogether, and to hold that the thing exists in the mind as a mere idea. ‘‘But the affirmation of a thing’’, says Ibn Mubārak, ‘‘constitutes the very existence of the thing’’. The idealist makes no such distinction as affirmation and existence. To infer from the above argument that the thing must be regarded as existing in the mind, is unjustifiable. ‘‘Ideal’’ existence follows only from the denial of externally which the As̱ẖ‘arite do not deny; since they hold that knowledge is a relation between the knower and the known which is known as external. Al‑Kātibī’s proposition that if the thing does not exist as external existence, it must exist as ideal or mental existence, is self‑contradictory; since, on his principles, everything that exists in idea exists in externally.
C. The Nature of Non‑existence
Al‑Kātibī explains and criticises the proposition, maintained by contemporary philosophers generally ‑I’ That the existent is good, and the non‑existent is evil’  The fact of murder, he says, is not evil because the murderer had the power of committing such a thing; or because the instrument of murder had the power of cutting; or because the neck of the murdered had the capacity of being cut asunder. It is evil because it signifies the negation of life a condition which is non‑existential, and not existential like the conditions indicated above. But in order to show that evil is non‑existence, we should make an inductive inquiry, and examine all the various cases of evil. A perfect induction, however, is impossible, and an incomplete induction cannot prove the point. Al‑Kātibī, therefore, rejects this proposition, and holds that ‘‘non‑existence is absolute nothing’’. The possible ‘essences’, according to him, are not lying fixed in space waiting for the attribute of existence; otherwise fixity in space would have to be regarded, as possessing no existence. But his critics hold that this argument is true only on the supposition that fixity in space and existence are identical. ‘‘Fixity in externally’’, says Ibn Mubārak, ‘‘is a conception wider than existence. All existence is external, but all that is external is not necessarily existent’’.
The interest of the As̱ẖ‘arite in the dogma of the Ressurrection‑the possibility of the reappearance of the non‑existent as existent‑led them to advocate the apparently absurd proposition that ‘‘non‑existence or nothing is something’’. They argued that, since we make judgements about the non existent it is therefore, known; and the fact of its knowability indicates that ‘‘ the nothing ‘‘is not absolutely nothing. The knowable is a case of affirmation and the non‑existent being knowable, is a case of affirmation. Al‑Kātibī denies the truth of the Major. ‘‘Impossible things’’, he says, ‘‘are known, yet they do not externally exist’’. Al‑Rzāī criticises this argument accusing Al‑Kātibī of the ignorance of the fact that the ‘essence? exists in the mind, and yet is known as external. Al‑Kātibī supposes that the knowledge of a thing necessitates its existence as an independent objective reality. Moreover it should be remembered that the As̱ẖ‘arite descriminate between positive and existent on the one hand, and non‑existent and negative on the other. They say that all existent is positive, but the converse of this proposition is not true. There is certainly a relation between the existent and the non‑existent, but there is absolutely no relation between the positive and the negative. We do not say, as Al‑Kātibī holds, that impossible is non‑existent; we say that the impossible is only negative. Substances which do exist are something positive. As regards the attribute which cannot be conceived as existing apart from the substance, it is neither existent nor non‑existent, but something between the two. Briefly the As̱ẖ‘arite position is as follows:
‘‘A thing has a proof of its existence or not. If not, it is called negative. If it has a proof of its existence. it is either substance or attribute. If it is substance and has the attribute of existence or non‑existence (i.e. it is perceived or not) it is existent or non‑existent accordingly. If it is attribute, it is neither existent nor non‑existent’‘.
NOTES AND REFERENCES
 ‘Muhammad Ibn Mubārak’s Commentary on Ḥikmat al’Ain, fol. 5a.
 Ḥusainīs Commentary on Ḥikmat al‑‘Ain, fol. 13a.
 Ibid. fol. 14b.
 Ibn Mubārak’s Commentary, fol. 8b.
 Ibid, fol. 9a.
 Ibn Mubārak’s Commentary, fol. 20a.
 Ibdn Mubārak. fol. 11a.
 Ibn‑Mubārak. fol. 11b.
 Ibid, fol. 4a.
 Ibn Mubārak’s Commentary, fol. 14b.
 Ibn Mubārak’s Commentary, fol. 15a
 Ibn Mubārak’s Commentary, fol. 15b.