Despite much scholarly effort, little is known about Roscelin of Compiègne. The only work that we can safely attribute to him is a letter he sent to Peter Abelard around 1119–1120. In this ill-tempered piece of writing Roscelin sets out to distinguish his position on the Trinity from that which Abelard was developing in his Theologia Summi Boni.
The problem for Roscelin and Abelard is to give an account of the distinction between the persons of the Trinity compatible with the unity of God. Roscelin notes that he has to navigate here between two heresies: Sabellianism, requiring such a unity in the singular substance of God that the distinction between the persons can be only verbal, and Ariansm, which distinguishes the persons as greater and lesser so as to constitute three distinct gods. Roscelin, in effect, accused his former student of Sabellianism, and so contributed to Abelard's being called before the Council of Soissons in 1121 and required to burn a copy of his Theologia Summi Boni and confirm his orthodoxy.
Roscelin's position is that the names Father, Son, and Holy Spirit pick out distinct items but that these exist in God with the unity of likeness and equality. Unfortunately he invokes authority rather than arguing for his theory. It has recently been suggested by author Constant Mews, however, that Roscelin depends on an account of the semantics of names developed in contemporary writing on grammar.
Our remaining information about Roscelin comes from two unsympathetic reporters. Abelard, in a letter written around 1119, complains about Roscelin's attack on him and recalls that long before, at the Council of Soissons in 1092, Roscelin had been charged with tritheism. From Saint Anselm we have two letters from 1090–1092, and the treatise De incarnatione verbi, written after the Council, in which Roscelin is said to have maintained that the persons of the Trinity are as separate from one another as three angels, or three souls. This is certainly not what he claims in his letter to Abelard, which may thus represent a refinement of his theory in response to Anselm's objections. In De incarnatione verbi Anselm characterizes Roscelin as a heretic in logic who holds that universal substances are nothing more than "puffs of air made with the voice," who cannot distinguish a body from its color, or a soul from its wisdom, and cannot understand how human beings are one in species.
In the middle of the twelfth century Roscelin was said to have been the first to have upheld the doctrine of words (sententia vocum ). From the information given, however, it is impossible to recover anything of his theory. We are told by John of Salisbury that he held that utterances themselves were genera and species. This is the position advocated in the Dialectica of Garlandus Compotista, written around 1115, which may provide our best guide to the views of Roscelin and those referred to at the time as the Vocales.
Appealing to Garlandus, Abelard's early writings, and various other texts, author John Marenbon has argued that vocalism in general and perhaps Roscelin's views in particular, developed out of what he calls the in voce reading of Porphyry's Isagoge and Aristotle's Categories. In this exegetical procedure, he suggests, theoretical commitment was suppressed in favor of reading the texts as simply about the relations between words.
Abelard confirms in his letter that Roscelin held that universals are in some sense words, and parodies him by saying he would have to read Scripture as claiming that Christ ate the expression broiled fish rather than the fish itself. It is unfortunately impossible to tell whether Abelard is constructing or reporting an argument when he reports, in his Dialectica, that as well as holding that species are words, Roscelin claimed that things do not have parts—so a wall is not part of a house. Perhaps what was really at issue were the questions that seem to have exercised Roscelin throughout his career: What counts as a thing and what is the nature of unity?
Marenbon, John. "Life, Milieu, and Intellectual Contexts." In The Cambridge Companion to Abelard. Cambridge, U.K.: Cambridge University Press, 2004.
Mews, Constant. Reason and Belief in the Age of Roscelin and Abelard. Aldershot U.K.: Ashgate, 2002.
Christopher J. Martin (2005)