Et ita in Deum non devenimus nisi arguendo. Argomentazioni sul primo principio nella falsafa, nel kalam e in Tommaso d'Aquino

The cosmological argument that concludes from the features of beings the necessary existence of a divine cause of them was set in ancient Greek philosophy. It resurfaces also in the Arabic philosophical and theological literature from the early ʿAbbāsid era onwards. A significant shift in emphasis however appears between the philosophical and the theological versions. In the philosophical literature, the cosmological argument takes the form of the transcendent causality of the First Principle imparted upon the terrestrial world through a series of intermediary causes that are arranged in a hierarchy of principles combining Neoplatonism and Aristotelianism. The muʿtazilite kalām, on the contrary, lays emphasis on God’s efficient causality, whose power produces everything that exists, with the features that every existent has. Committed to atomism, the muʿtazilite cosmology paves the way to the occasionalism of the ašʿarite kalām, which in turn foreshadows the Ghazalian critique of causality in the Tahāfut al-falāsifa. In the Arabic-Islamic philosophy of the 10th and early 11th centuries, on the contrary, the cosmological argument takes the form of an inference that establishes the necessary existence of a first principle from the typical features of being: movement and contingency. This paves the ground for Thomas Aquinas to mention Avicenna as a philosopher who shares with him the idea that we reach sure knowledge about God only through reasoning: in Deum non devenimus nisi arguendo.