restricted access Aquinas, the Plotiniana Arabica, and the Metaphysics of Being and Actuality
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Aquinas, the Plotiniana Arabica, and the Metaphysics of Being and Actuality

Historians of Western philosophy have long thought that the Liber de causis played an important role in the formation of metaphysical thinking in the Latin West following its translation in the mid-twelfth century.1 This was clearly based on the incorporation of this work into required philosophical studies at the University of Paris and elsewhere as well as on the frequent citation of or even commentary on the doctrines of the Liber de causis. The text generated at least 27 different Latin commentaries and is extant today in Latin in nearly 240 manuscripts.2 Doctrinally, the text played a very significant role in the thought of philosophers and theologians of the thirteenth century, particularly with its notion of being as alone caused in things by God, who is described as esse tantum and ens primum.3 Both notions were used by Thomas Aquinas as early as the time when he wrote his De ente et essentia, in which he asserted that God’s essence and quiddity are his being and that the notion of God as pure being or esse tantum is not to be understood as formed by abstraction upon the [End Page 217] consideration of ens commune.4 But exactly how such doctrines are to be understood and how they fit into the historical development of philosophy from ancient times through the medieval period has not been clear. Such was the case in part because of the lack of a critical text and in part because of the lack of studies of the Liber de causis in relation to sources.5 Without such tools the sense of this work’s doctrines could not be grasped in their proper historical context, and the role of the Liber de causis in the history of philosophy could only be a matter of tentative speculation.

Scholars pursuing a comprehensive understanding of the history of philosophy seek to incorporate into their work all that is available from historical, textual, and philosophical studies. A good example of this is perhaps the approach of Etienne Gilson to the question of the Thomistic doctrine of essence and existence in relation to developments in the history of philosophy in ancient and medieval times. In both L’Etre et l’essence6 and the earlier Being and Some Philosophers Gilson sharply contrasts the philosophy of Plotinus with that of Thomas Aquinas on the nature of the first principle of all, stressing that the metaphysics of Plotinus is a metaphysics of the One or Unity, a kind of Henology, while holding that for Thomas Aquinas metaphysics deals with being or esse and that the first principle is Esse itself.7 Such an understanding of Aquinas and Plotinus would appear to be well founded.

Yet while Aquinas incorporates much of the philosophical reflection on the nature of being found in the work of Aristotle and Parmenides, he also transcends their reflections in his presentation of his understanding of the divine nature. For Parmenides being is to be regarded as indivisible, continuous,8 motionless, ungenerated, imperishable, without beginning or end, and (perhaps most importantly for the history of metaphysics) finite; “for strong Necessity holds it firm within the bonds of the limit that keeps it back on every side, because it is not lawful that what is should be unlimited; for it is not in need—if it were, it would need all.”9 This “strong Necessity” is not the result of something [End Page 218] outside being, for outside it nothing is; rather, Being is self-limited and everywhere equal within its own bounds because of its very nature.10 For Aristotle, too, being is finite, although in a different sense; and he follows Plato in maintaining the primacy of form in his understanding of being. Plato and Aristotle are both dependent on the notion of the concomitant nature of being and thought found in the Poem of Parmenides.11 For both Plato and Aristotle the relation of being and thought yielded a conception of being as form and intelligibility. Of course, for Plato forms existing separate from the material things of the world have...