Abstract

In his masterwork De Trinitate, Augustine claims there is no real difference between the notions of essentia and substantia, even if the former better express the unity of God and if the latter is more commonly used. Still, a useful philosophical distinction can be drawn from Augustine’s use of the two terms : since substantia may contain a possible conception of potentiality, Augustine prefers essentia to avoid any implication of multiplicity inside the Trinity. John Scottus Eriugena receives Augustine’s influence but elaborates on it through his work on some Greek fathers, notably Pseudo‑Dionysius the Areopagite, Gregory of Nyssa and Maximus the Confessor. In his dialogue Periphyseon, Eriugena merges Latin and Greek trinitarian vocabulary and doctrine ; according to him, causality is at the core of trinitarian relations, for even in the godhead, the Father is the only true anarkos, uncaused, the Son and the Holy Spirit being caused by him. This is particularly evident in the created image of the Trinity, i.e., the human soul. For the Irishman, the Augustinian gnoseological triad coincide with the Dionysian ontological triad. Through its trinitarian form, human mind is both capable of understanding God and manifesting his causal relation to created nature. Thus, Eriugena blends Augustine’s careful ontological distinction in a Greek neoplatonic triadic conception.