In this presentation, Filipa Afonso will examine whether John Scottus Eriugena, a 9th century Christian philosopher, can be considered an idealist. To do so, she will begin by addressing the concept of idealism itself – an ambiguous term that encompasses several distinct theories, such as Platonic idealism, empirical idealism, transcendental idealism, and absolute idealism.  Next, she will focus on the main tenets of Berkeleyan idealism—namely, that esse est percipi (to be is to be perceived), and, consequently, that neither material things nor material perceivers exist. With these criteria in mind, she will explore whether Eriugena’s philosophy aligns with idealism. Specifically, through an exposition of Eriugena’s theory of substance (as a concept of the mind), bodies (as coalescences of incorporeal properties, with no subjacent matter), and place, she will argue that, based on the immateriality of God, the infinity of God, and the rational nature of the human mind, nothing can exist, either materially, outside God’s mind, or outside the human mind.