The problem related to the origin of the concept of actus essendi constitutes one of the central themes in the history of ancient philosophy, and is one of the most important in the process known as Translatio studiorum. The idea according to which Thomas Aquinas was the first to consider this concept has been contrasted to the idea that actus essendi had already been present in Neoplatonism. In fact, the concept of \u201cbeing\u201d in Thomas Aquinas\u2019 philosophy has been interpreted in many different ways over the years, especially in relation to Aristotle\u2019s concept of being. In his book about being according to Thomas, G. Ventimiglia recognizes three generations within the historiography on Thomistic ontology. The first generation, begun by R. Garrigou-Lagrange, lasted until the end of the 1930s and maintained that the being of Thomas equalled Aristotle\u2019s. During the second generation, lasting from the beginning of the 1930s till the end of the \u201950s and whose main exponent was E. Gilson, the being of Thomas is seen as the actus essendi. These scholars therefore interpreted it as a completely new and original concept compared to both Aristotle\u2019s being and the Neoplatonic school of thought, by which Thomas may have been influenced. Lastly, the third generation, in which Thomas\u2019 concept of being is considered to be unoriginal, having been elaborated within the world of Neoplatonism, originated at the beginning of the 1970s and lasts yet today. W. Beierwaltes and K. Kremer, among others, have lead this final generation. However, together with Ventimiglia, it is necessary to recognize the importance that the publication of two other works had on the assertion made by the \u201cthird generation\u201d. These works are P. Hadot\u2019s volume on Porphyre et Victorinus, published in 1968 and Beierwaltes\u2019 book entitled Platonismus und Idealismus, published in 1972. In the latter\u2019s book, the author demonstrates that the identification of God with being had been made by Plutarch and Porphyry as well as by Philo of Alexandria, Gregory of Nazianzus, Gregory of Nyssa, Victorinus and Augustine. In Hadot\u2019s volume, together with the observation that this identification had been expressed in Neoplatonism, also the definition of being as act is traced back to the same period.
In the paper it is discussed the section of Hadot\u2019s study which appears in the appendix of the second volume, containing the text and the translation of the fragments of the anony\uacmous commentary to Plato\u2019s Parmenides. It also considered the introductory essay added in the Italian translation of this section. It is thanks to Hadot and the exponents of Ventimiglia\u2019s \u201cthird generation\u201d that the communis opinio, according to which the concept of actus essendi can be found first in the philosophy of Thomas, was disproved. Hadot in particular demonstrated that the notion of \u201cact of being\u201d originated from both the anonymous commentary to the Parmenides by Plato, which he attributes to Porphyry, and the Enneads by Plotinus. This paper will first examine the fragments of the commentary in order to show that in it may be found both the identification of God with being and the concept of being as actus essendi. An analysis of Enneads VI 8, 7 will follow. This is one of the passages in the work by Plotinus which most deserves to be considered in order to verify the effective anticipation of Neoplatonism in a doctrine that has traditionally been considered of Thomistic origin. Finally, of particular interest is the comparison between being as interpreted by Neoplatonism, especially by Plotinus, and act as conceived by Aristotle, unanimously recognized as its discoverer
