In Aristotle, substance, being specified in Z17 as cause and principle, is to be understood according to the analogical theory of principles and causes, namely form, matter and privation. These three causes involve potentiality and actuality, since form, privation, and the compound substance are in actuality, while matter is in potentiality. ≪What a substance is≫ depends on the connection between these three principles. In order to grasp the meaning of this connection, one has to put the analogical theory of principles back in its context, where previous theories on contraries (Plato’s theory included) are amended.The amendment of previous theories of principles relies on positing a third term, matter, between both opposites, i.e. form and privation. The implied distinction between matter and privation allows an understanding of generation which makes it compatible with substance. While generation removes privation, substance as form gives shape to matter, final matter and shape being identical to one another. Predication of matter by form supplies a relevant pattern for considering the relationship between matter, form and privation. At the same time, predication of matter by form provides both a renovated theory of opposites and a new theory of form as a cause, i.e. a theory of form as actuality.

This paper deals with the Aristotelian notion of topical matter (ὕλη τοπική) mentioned in a few passages of the Metaphysics and ascribed to the celestial bodies. Taking into account the metaphysical context of each occurrence of this notion, it tries to determine for what metaphysical use this notion has been developed and what impact it has on the ousiological analysis of the celestial substances. It suggests that the notion of topical matter, although intended to provide a convenient tool that makes possible a metaphysical, i.e. universal study of sensible substances, by allowing to subordinate every sensible substance to similar principles, in fact prevents celestial substances from being defined as ordinary hylomorphic compounds and leads to conceive them as a particular type of substances.

The initial dilemma. I.1. The gradual rise of the Metaphysics. I.2. A bold contribution from textual history. I.3. A new perspective on late ancient commentaries. I.4. First philosophy or Metaphysics? I.5. Can tradition be ignored? II. ‘Being’ and οὐσία at the core of Aristotle’s theoretical research. II.1. Ontology as a science of ‘being’ in Aristotle: “What is X?” in the foreground. II.2. The first caveat: the copula function of Aristotle’s ‘being’. II.3. The definite article τό as quotation marks before the flexed forms of ‘be’: τὸ ὄν, τὸ εἶναι, τὸ ἔστιν. II.4. Further explanations about Aristotle’s ‘being’. III. Οὐσία, the core of Aristotle’s theoretical philosophy. III.1. οὐσία and the criterion of pre‑eminence as Plato’s legacy. III.2. The dialectical roots of ontology. III.3. οὐσία from Zeta to Lambda. III.4. οὐσία as essence and οὐσία as substance. III.5. οὐσία as a syntactical core; the word’s etymology. III.6. οὐσία as the first sense of being in Aristotle’s first philosophy. III.7. Ontology as science, science of the science. IV. Historicizing: the semantic gap. IV.1. Editorial tradition: ontology and οὐσία as a fil rouge in the order of Metaphysics books. IV.2. οὐσία in the first century B.C. IV.3. οὐσία by Alexander of Aphrodisias. IV.4. Metaphysics and its purpose: the role of the Lambda book. IV.5. Being and οὐσία: a relationship lost over time. IV.6. The Aristotelian tradition as a way to cooperation.

In the Corpus Aristotelicum there are two different theories of substance which apply to the sublunary world. The first theory is found in the Categories and selects the individual concrete as a primary substance (πρώτη oὐσία). The second is found in the Metaphysics (mainly in book Z) and selects the Form (εἶδος) and the Essence (τὸ τί ἦν εἶναι) as a primary substance. Most of the interpretations of modern Aristotelian scholarship claim an inconsistency. They suggest that if at all Aristotle has a theory of substance, then it is either the substance theory of the Categories or the one of the Metaphysics but not both of them. The supposition of all these interpretations is that Aristotle’s theory of substance is unambiguous and that there can be only a single primary substance. These interpretations suppose that the theory of substance is applicable only to a single domain, namely to ontology.In my paper I argue that this supposition is false. I suggest that Aristotle’s theory of substance is applicable not only to ontology but also to the domain of determinology whose meaning is explained in the paper. The theory of substance of the Categories applies to ontology whereas the one of the Metaphysics applies to determinology. The two theories are consistent with each other in a way that there are two commensurate sorts of primary substance: the individual concrete as the ontological primary substance of the Categories and the Form‑Essence as the determinative primary substance of the Metaphysics.Furthermore, I claim that Aristotle’s concept of substance is manifold and flexible. The concept evolves and is expanded in the Metaphysics. It is manifold because his theory of substance has a certain structure which includes the following three criteria for selecting a primary substance: (1) subjecthood viz. being a subject (τὸ ὑποκείμενον), (2) independence (τὸ χωριστόν) and (3) (well) determined individuality (τὸ τόδε τι). Aristotle’s concept of substance is flexible because these criteria do not have an absolute signification per se but are general and relative. They get a final signification when they are applied either to the ontology in the Categories or to the determinology in the Metaphysics. Their application to a certain domain establishes a theory of substance according to the domain in question and selects a primary substance according to the same domain. Aristotle’s concept of substance is flexible also because in the Metaphysics he enlarges his first concept of substance expressed by the three criteria by adding a new sort of substancehood expressed by the idion criterion.

The idea that defines quiddity – independence or neutrality in relation to the modalities of existence – allows Avicenna not only to speak of a duality in the being of existing things, but also to use apparently logically incompatible notions to qualify quiddity: that of reality (or truth), on the one hand, and that of possibility (or falsity), on the other. The very conception of the independence of quiddity – which lets us consider quiddity as a separate element in the existing thing – can be recognized in the resolution of the doubt that concludes the Maqāla fī l‑tawḥīd of Yaḥyā ibn ‘Adī (d. 974). A comparison between Avicenna’s discussion of quiddity in his Metaphysics and the discourse of Yaḥyā ibn ‘Adī confirms the idea that this Christian philosopher and theologian who was active in Baghdad in the tenth century could have played an important formative role in the ontology of the great Persian philosopher.

This article aims to consider the permanence of the Greek term ousia, sometimes transcribed as usia, during the early Middle Ages, when the translation by substantia was imposed. We consider two figures of the Carolingian period, John Scottus Eriugena and Ratramnus of Corbia. We suggest that the word ousia/usia may express aspects of being that the Latin term substantia does not support.

The article shows that Thomas Aquinas in many of his works (De ente et essentia, Summa theologiae, Sententia in Aristotelis Metaphysicam) interprets the passage Aristot. Metaph. II 1, 993 19‑31, as expounding a theory of degrees of truth and of being, which is not the true Aristotelian doctrine. This is due to the fact that he interprets ≪the eternal things≫, mentioned by Aristotle in that passage, as the heavenly bodies, and their principles as the unmoved movers, while Aristotle is speaking of the eternal truths, i.e. the truths of scientific knowledge, and of their principles, which are the axioms. The origin of Thomas’ interpretation is the commentary by Alexander of Aphrodisias, which Thomas knew via Averroes.

The Stoics try to demonstrate, in a theoretical context, more than any other philosophy, the link unifying the parts with the whole, in all areas of existence; namely, from man to divine reason, from god to nature – a tautological link in some cases – from matter to logos or creative pneuma. This unifying bond – hexis or continuity – guarantees the attachment between bodies which are in a state of sympathy (or interaction) which also constitutes their existence. It remains to seek the meaning of this notion; draw on its etymology: according to Bailly’s dictionary, the term hexis in Greek means among other meanings: action of possessing, possession. And according to the dictionary of L.‑S.‑J., hexis (proper noun) derives from the future of the verb ἕξω, from the verb ἔχω, (to have, to possess); in its intransitive form refers to a permanent condition, namely to an act, which results from practice.In order to make an attempt to define this concept or to orient its function, it seems appropriate for us to do some research – we could say historical –, consulting texts prior to Stoicism, examining its place and the nuances it takes in different contexts and finally, follow its interpretation where, according to philosophical approaches, it sometimes means disposition, habit, or situation. Nevertheless, the Stoics give this term an original meaning, different from the one that was granted to it until then. It is the hectic pneuma or the tension (tonos) prevalent in the universe. In this perspective, we will try to define its function and compare it with the notion of hexis in Aristotle, where it acquires the meaning of metaxy, in his Metaphysics, Δ, 1022b12.

Porphyry’s Expositio per interrogationem et responsionem can help us to understand some obscure passages of chapter seven of Aristotle’s Categories, focused on the relative (πρός τι). The Porphyrian analysis of πρός τι presents indeed developments which are both useful for the understanding of the Aristotelian text and very innovative too. First, we can mention the general Porphyrian thesis according to which categories are predicates. This theory fits very well with πρός τι, which are predicates corresponding to properties that subjects only possess because of an observed reciprocal relationship. This brings us to the second novelty of Porphyry’s analysis, really important for modern developments of the notion of relation, namely the difference between σχέσις and πρός τι, which depends on it. Finally, we will mention the important Porphyry’s contribution to the understanding of a particularly obscure issue concerning the relationship between the two definitions of πρός τι that Aristotle provides. Porphyry points out the Platonic origin of the first definition, without dismissing it though: instead, he will just consider it too vast and encompassing the true πρός τι, object of the second definition.

This article examines Averroes’ interpretation, found in his Long Commentary on the De Anima, of a famous passage in Aristotle’s De An. III 5 (430a14‑15) which presents the intellect “producing all things, as a kind of positive state (hexis), like light”. Averroes, clearly heir to Alexander of Aphrodisias for whom hexis refers not to the intellect “agent” itself but to its product, defends nevertheless, via the comparison with light, the conception of the agent intellect (a substance purely in act by itself ) as an hexis, which leads us to the inevitable consequence that the agent intellect is the prime object of the material intellect, acting as a condition for all subsequent thoughts.

The present paper aims at presenting Averroes’ doctrine of act and potency in the framework of his general conception of metaphysics as a science. By tracing the origins of his doctrine back to Alexander of Aphrodisias, it shows that Averroes conceives act and potency as concomitant attributes of being qua being and as terms πρὸς ἕν and ἀφ’ ἑνός. According to this reading, the study of these two notions, considered as such, constitutes an essential step in Averroes’ metaphysical project, whose ultimate goal is to account for the essence of the first of all forms: God.

Οὐσία in Numenius: a notion which is progressively elaborated: Analysis of the difficulties linked to οὐσία and ἰδέα in fragments 22 F, 24 F and 28 F (fr. 14, 16 et 20 dP). In the Περὶ τἀγαθοῦ, Numenius refines his definition of οὐσία step by step. He uses the word at first as a synonym of τὸ ὄν (15 F) and as another designation of being. Then, he associates it to the ἕξις when he refers to the specific οὐσία which possesses science (22 F): in all likelihood, this οὐσία is the intellect as the essence common to God and Man in the possession of science. Finally, Numenius gives οὐσία two aspects or sides which, in our opinion, represent two manners of conceiving the intelligible it constitutes: on the one hand, οὐσία comes from Being itself (the Good) and seems to represent the eidetic predicates or what we could name the “fundamental intelligibility”, a state in which the form is not determined yet, but which gives it the status of a real being ; on the other hand, οὐσία is the product of the second god and intellect and the determined aspect of the previous one, which makes it possible to distinguish the forms one from the other. In this last case, Numenius seems to name οὐσία more specifically ἰδέα, even if both words are elsewhere synonymous and used to refer to the two aspects previously mentioned according to the context in which they are employed. The paper presents the analysis of fragments 22 F, 24 F and 28 F from which we arrive at this interpretation. The distinction between two manners of conceiving οὐσία makes it possible then to discover two levels in the Being at the origin of each of them: Being itself (αὐτοόν which is the Good itself, αὐτοάγαθον) and the ≪second≫ or ≪just≫ Being, constituted by the good demiurge which is probably the “One who is good par excellence”. From there, two ways of conceiving ἰδέα also appear: on the one hand, ἰδέα is synonymous with οὐσία, then it refers to the second aspect of οὐσία, the determined one; on the other hand, it can also refer to the level of Being which is the Good when, in fragment 28 F, it is conceived as a form and probably as the Form par excellence identified with the intellect which this Good is itself.

At the end of Treatise 38 (VI 7), Plotinus presents an original analysis of the activity of the intellect. The intellectual activity of the soul cannot produce its object and thinks what is in the Intellect from which it comes. On the contrary, the Intellect produces its object (οὐσία) and its intellection is not the act of a substrate (ὑποκείμενον), as in the preceding case. In this context, Plotinus uses, to account for this particular form of intellect, a very rare notion in his work, that of συνυπόστασις. In our opinion, its use is at the origin of a true explanatory model that Plotinus uses in particular in Treatise 39 (VI 8) to think how the One can be what he wants to be. The use of this notion can therefore help us understand the meaning of freedom and will attributed to the first principle.

In his critic of the doctrine of Bardaisan († 222), Ephrem the Syrian († 373) devotes a lot of space to reflection on the meaning of the terms ītutā and ītyā (plural ītyē) which, as he denounces, are used inaccurately by his opponent. These Syriac terms can be translated by “being” or “essence”, but also by “substance”. This observation leads us to propose the comparison with the Greek term οὐσία, taking into account many difficulties raised by its uses in theological discourse. The article is devoted to the analysis of the uses of the terms ītutā and ītyā ‑ by Ephrem and by Bardaisan ‑ in their different ways of describing the divine essence. This comparison reveals the peculiarities of the two systems of thought and also their connections with the Greek philosophical doctrines.

The rediscovery of the Hellenic philosophy, but also of the Patristic thinking is a typical feature of Thomistic thought, which consists of a new synthesis of Hellenism and Christianity that raises anew the issue of the relation between Christianity and philosophy as a focal point of medieval philosophy. Acknowledgement of Hellenic Patristic thought that focuses primarily on man as an inseparable union of body and soul, joined in a whole, has been a determining factor in the Thomistic approach of being, through the distinction between a person (or hypostasis) from essence (or nature). Through this distinction and because of the Aristotle’s hylomorphism, the notion of ‘person’ is placed in the field of individuality and the unity of the human composite. The metaphysical notion of a person as individual, complemented by the notion of “relation” is directly related to the ontological unity of human nature and is founded upon the metaphysical notion of “essence” (substance).