A Ninth-Century Arabic Logician on: Is Existence a Predicate? Nicholas Rescher Journal of the History of Ideas, Vol. 21, No. 3. (Jul. - Sep., 1960), pp. 428-430. Stable URL: http://links.jstor.org/sici?sici=0022-5037%28196007%2F09%2921%3A3%3C428%3AANALOI%3E2.0.CO%3B2-6 Journal of the History of Ideas is currently published by University of Pennsylvania Press.
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AL-FARABI
ON LOGIC
429
has a p r e d i ~ a t e . ~T o my mind, both of these judgments are in a way correct, each in its own way. This is so because when a natural scientist who investigates perishable things considers this sentence (and similar ones) i t has no predicate, for the existence of a thing is nothing other than the thing itself, and [for the scientist] a predicate must furnish information about what exists and what is excluded from being.6 Regarded from this point of view, this proposition does not have a predicate. B u t when a logician investigates this proposition, he will treat i t as composed of two expressions, each forming part of it, and it [i.e., the composite proposition] is liable t o truth and falsehood? And so it does have a predicate from this point of view. Therefore the assertions are both together correct, but each of them only in a certain way. Consideration of the question " I s ' exists ' a predicate? " and of the logical issues involved in it thus goes back a t least t o the I X t h century. Further, al-FBrbbi's insistence t h a t the attribution of existence to a n object adds nothing to its characterization. and provides no new information about it, effectively anticipates Kant's thesis that: " Sein ist offenbar kein reales Pradicat, d. i. ein Begriff von irgend etwas, was zum Begriffe eines Dinges hinzukommen konne." A word must be said as t o the problems which occasioned al-Fbrbbi's treatment of the matter. Al-FBrBbi, followed in this regard by Ibn Sing (Avicenna), wants clearly t o distinguish the existence (huwiya) of a thing from its essence ( r n d h i ~ a ) . B ~ ut if ' exists ' is a predicate, then the existence of a thing would seem t o become one of its properties, and could thus be held t o be among the attributes constituting its essence. T o preserve a clear distinction between essence and existence, al-Fbrbbi denies that existence is a predicate (i.e., a n informative predicate) .lo 5 By ' ancients,' the Islamic philosophers intend the Greek thinkers and their Hellenistic expositors, by 'moderns ' the philosophers who used Arabic. Compare Averroes: " The ancient philosophers considered the First Principle . . . as a simple existent. As to the later philosophers in Islam, they . . . [also] accept a simple existent of this description." Tahafut al-Tahafut, translated by S. Van den Bergh LOxford, 19541, I, 237. 6That is to say, the predicate must give information regarding the nature (mcihiya, ' what '-ness, quidditas) of the thing in question. The existence of a thing (its huwiya, ' that '-ness, esse) is not a part of its essence. 7 Grammatically, ' Man exists ' is a complete sentence, with a grammatical subject, ' man,' and a grammatical predicate, ' exists.' Thus due to close parallelism between the logical and the grammatical relations (especially in Arabic) al-F8ribi unhesitatingly classes ' exists ' as a legitimate grammatical (or logical) predicate. Even Kant agrees with this, affirming that: " zum logischen Pradicate kann alles dienen, was man will." Compare also Averroes' view that "the word 'exists ' does not indicate an entity added to its [i.e., a thing's] essence outside the soul, which is the case, when we say of a thing that it is white." Tahafut d-Tahafut, 11, 118. On their view, these coincide only in God. 1°Avicenna, however, held that existence is a predicate, and therefore, save with God, necessarily an accident (so that it would not be an essential property). Averroes, who denied the validity of the distinction between essence and existence,
430
NICHOLAS RESCHER
The historical origin of the distinction between essence and existence has not yet wholly emerged from obscurity. In her masterly study of La Distinction de Z'Essence et de Z'Existence dJapr8s I b n Sin6 (Paris, 1937), Mlle. A. M. Goichon puts the matter as follows: Ibn Sin8 la recevait [i.e., la distinction de l'essence et de l'existence] de FBrBbi qui l'avait entrevue, mais sans lui donner tout son ampleur. Tr6s probablement, tous deux l'ont considerhe comme deduite des principes aristoteliciens, car ils n'en parlent jamais comme d'une dkcouverte. Elle fait presque figure de lieu commun, et nulle rkfkrence ne perrnet d'afirmer quel texte la leur a inspir6e. Peut-&re les recherches dans les manuscrits, les traductions, les gloses anciennes, permettront-elles de determiner la source. Pour le moment les mat6riaux nous manquent . . . et nous ne pouvons remontrer avec certitude plus loin que F8rbbi. (131-132.) There is no doubt, however, that the distinction was inspired by Aristotle, and took definite form in the hands of his commentators and expositors. There is nothing in the Arabian distinction between mcihiya and huwfya that could not arise naturally out of explicative glosses on the following passage of the Posterior Analytics: H e who knows what human-or any other-nature is, must know also that man exists; for no one knows the nature of what does not exist . . . . But further, if definition can prove what is the essential nature of a thing, can it also prove that it exists? And how will it prove them both by the same process, since . . . what human nature is and the fact that man exists are not the same thing? Then too we hold that it is by demonstration that the being of everything must be proved-unless indeed to be were of its essence; and since being is not a genus,ll it is not the essence of anything. Hence the being of anything as fact is matter for demonstration; and this is the actual procedure of the sciences, for the geometer assumes the meaning of the word triangle, but that it is possessed of some attribute he proves. What is it, then, that we shall prove in defining essential nature? Triangle? I n that case a man will know by definition what a thing's nature is without knowing whether it exists. But that is impossible. (An. Post, 92133-18 [Oxford translation] ; cf. also 93a ff .) For Arabic philosophy then, the question " I s ' exists ' a predicate? " arises, not from considerations relating t o the Ontological Proof, but out of a desire t o sharpen and clarify the Aristotelian distinction between the eseence of things on the one hand, and their being or existence upon the other. Not the ontological argument, but the increasing systematization of certain concepts of Aristotle's logic occasioned al-li'brbbi t o take up the problem of existence as a predicate. Lehigh University. and argued against Avicenna on this ground, also condemned Avicenna's mistake that the existence of a thing is one of its attributes." Tahafut al-Tahafut, I, 236; see also 11, footnote 237.4. 11Cf. Metaph. 998131424, 1045a34-68. Nor, on Aristotle's view, is being an attribute of things (An. Post., 90a2-4). This, in effect, amounts to al-Bbrbbi's point that existence is not an informative predicate. Aristotle does, however, insist that being is a predicate (Metaph. 1053b17-21), but his view and its grounds find accommodation in al-Fbrbbi's assertion that existence is a logical predicate.
