Between Greek and Latin: Eriugena on Logic

Chapter 4 Between Greek and Latin: Eriugena on Logic

Christophe Erismann

1 Introduction

The close and mutually beneficial relation between logic and theology – meaning both the use of logic in order to strengthen theological discourse and the improvement of logic by theologians – is not an invention of the 9th century. When John Scottus Eriugena intervenes in the field of “Christian” logic, he does so after several centuries of such an established tradition of rational theology. Already in the 4th century, Marius Victorinus (ca. 280–365) was not only a translator of logical texts – including Porphyry’s Isagoge and, according to Cassiodorus, Aristotle’s Categories – but also an interpreter of Aristotelian logic. In particular, he contributed to expanding the use of logic in theological contexts. In this he was a true initiator, whose work revealed to the Latins how logic could be put to the service of theology, a practice which was common in the Greek world, where participants in Christian theological controversies regularly had recourse to logic. Boethius (ca. 470–524) is the author who un- doubtedly did the most to promote the diffusion of Aristotle’s logic in the Latin world. Boethius translated the Categories, preceded by Porphyry’s Isagoge, the On Interpretation, the Prior Analytics, the Topics, and the Sophistical Refuta tions. He composed two commentaries on the Isagoge, one on the Categories and two on the On Interpretation. Boethius also promoted logic in a theological context. His theological treatises constitute a lesson in the methodology of rational theology that was to be highly influential. The use of logic in theology was widespread among Greek theologians contemporary with Boethius. In his Opuscula sacra – first and foremost the On Trinity and Against Eutyches and Nestorius – Boethius1 offered a model of rational theology based on logic that medieval thinkers, including especially Eriugena,2 took as a model. The Opus cula sacra are a model of the application of dialectic to theology. Boethius uses

1 Brian Daley, “Boethius’ Theological Tracts and Early Byzantine Scholasticism,” Mediaeval Studies 46 (1984), 158–91. 2 See Giulio d’Onofrio, “Dialectic and Theology: Boethius’ Opuscula sacra and Their Early Me- dieval Readers,” Studi Medievali 27 (1986): 45–67; and idem, “Giovanni Scoto e Boezio: Tracce degli Opuscula sacra e della Consolatio nell’opera eriugeniana,” Studi Medievali 21 (1980): 707–52.

© koninklijke brill nv, leiden, �� | doi:10.1163/9789004399075_006 94 Erismann the Aristotelian logical tradition as it had developed within Neoplatonism to solve theological problems and to tackle heresy. Boethius himself took his in- spiration from Aristotle’s idea of science. His theological method consists in the application of the logical rules of definition and demonstration to those elements of the divine nature that are accessible to human rational under- standing. The contribution of Cassiodorus (ca. 485-ca. 580), a Latin politician and writer who founded the monastery of Vivarium, is remarkable too. His Institutions [Institutiones] provide an influential summary of logic. His ma- jor work, a commentary on the Psalms [Expositio psalmorum], defends a par- ticularly remarkable theoretical use of logic. A commentary on the Psalms is, according to Cassiodorus, the adequate place for teaching all the liberal arts, including dialectic, that is logic. Insofar as Aristotle’s logic is concerned, the focus is on the use of the theory of the syllogism. Cassiodorus makes a great effort to convince his readers that it is orthodox (fas est) to deal with syllogisms in the Scriptures.3 Latin patristic thought, just like Greek patristic thought, sets up a critical yet fruitful dialogue with philosophical thought, questioning the relevance and the limits of the use of logic in theology. The two homonymous treatises On the Trinity by Augustine and Boethius are excellent examples of this phenomenon. The question is basically the following: can we use the ten Aristotelian categories for speaking when referring to God? This problem, formulated clearly by Boethius, is the Christian version of an old problem. It is nothing else than a Christianized variation of Dexippus’s first aporia on essence – can essence constitute a unique genus which includes both the sensible essence and the intelligible essence? – and of Plotinus’s enquiry about the universality of the Categories and the inclusion of intelligible realities in Aristotle’s scheme. In Chapter four of his de Trinitate, Boethius states first that there are a total of ten categories which are predicated universally of all things (Decem omnino prae dicamenta traduntur, quae de rebus omnibus universaliter praedicantur […]),4 If we apply the question of predication to God, the categories which can be predicated are modified and change their meaning entirely (At haec cum quis in divinam verterit praedicationem, cuncta mutantur quae praedicari possunt 173.181–2). The explanation for this modification is the fact that substance in God (substantia in illo) is not truly substance (non est vere substantia) but be- yond substance (sed ultra substantiam 173.184). Boethius thus establishes the

3 Michel Ferré, “Cassiodore, professeur de dialectique dans le commentaire sur les Psaumes,” Philosophie antique 4 (2004): 95–129. 4 Boethius, De Consolatione philosophiae; Opuscula theologica, ed. Claudio Moreschini (Munich: 2000), 173.174–5.