Life. Roscelin of Compiègne was born either at
Compiègne, or as is more probable, in lower Brittany, about the
middle of the eleventh century. He studied at Soissons and at Rheims.
In 1098 he became canon of Compiègne and taught in that city,
and later at Besançon and at Tours. Among his many disciples was
Abelard. On account of the great number of those who flocked to hear
him and partly also on account of the development which he gave to
Aristotle's dialectical doctrines, Roscelin was styled Novi Lycaei
Conditor. He died about 1100.
Sources. It appears that Roscelin did not commit his doctrines
to writing, contenting himself with promulgating and defending them
orally. There has come down to us, however, a letter addressed by him
to Abelard  dealing chiefly with Roscelin's Trinitarian doctrine.
Apart from this document we have no sources of information except the
statements of Anselm, Abelard, and John of Salisbury, who
were Roscelin's opponents. Monograph: M. Picavet, Roscelin d'apres
la legende et d'apres l'histoire (Paris, 1896).
From the sources mentioned in the preceding paragraph we derive the
following points of doctrine:
1. Roscelin taught that universals are mere flatus vocis. Anselm 
says: "Illi utique nostri temporis dialectici, imo dialectice
haeretici, qui nonnisi flatum vocis putant universales substantias. . .
." John of Salisbury refers the same opinion to Roscelin by name:
"Alius ergo, consistit in vocibus, licet haec opinio cum Rucelino suo
omnino jam evanuerit."  From these passages we infer that Roscelin
was a nominalist, although the expression flatus vocis is
obviously the phrase used by his opponents rather than by Roscelin
himself to describe his doctrine.
 De Fide Trinitatis, Cap. 2.
 Metalogicus, Lib. II, Cap. 13.
2. Consistently with his nominalistic doctrines that the genus and
species have no substantial unity, -- that the union of individuals in
the genus or in the species is a mere fabrication of language or at
most the work of thought, -- Roscelin maintained that the distinction
of the whole and its parts is also the result of mere mental analysis.
Thus Abelard declares: "Fuit autem, memini, magistri nostri Roscelini
tam insana sententia ut nullam rem partibus constare vellet, sed sicut
solis vocibus species, ita et partes adscribebat";  and elsewhere, 
after describing his former teacher as "pseudo-dialecticus et
pseudo-christianus," he argues that when the Gospel tells us that Christ
ate part of a fish Roscelin would be compelled to maintain that Christ
ate part of a word.
 Ouvrage inéd., p. 471.
 Epistola XXI ad Episcopum Parisiensem.
3. Roscelin did not hesitate to apply his nominalism to the doctrine
of the Blessed Trinity.  The one nature in three divine persons
must, he argued, be a universal. Now, the universal has no real
existence. Therefore, he concluded, the oneness of the divine nature is
not real (tritheism). That Roscelin held this doctrine is
evident from the references of St. Anselm,  from Abelard's epistle to
the bishop of Paris, and from Roscelin's letter to Abelard.
 It is by no means certain that this is the application which
 Cf.De Fide Trinit., Cap. 1.
4. It appears from the testimony of St. Anselm that Roscelin either
taught or was suspected of teaching the tenets of sensism. In De Fide
Trinitatis, Cap. 2, Anselm is evidently speaking of Roscelin's school
when he says:
In eorum quippe animabus ratio, quae et princeps et judex omnium debet
esse, quae sunt in homine, sic est in imaginationibus corporalibus
obvoluta ut ex eis se non posset evolvere nec ab ipsis ea quae ipsa
sola et pura contemplari debet valeat discernere.
In the fifth chapter of the same treatise allusion is made to the
danger of passing from sensistic empiricism to rationalism:
"Nolentes credere quod non intelligunt, credentes derident."
Condemnation of Roscelin. Scholastic philosophy contained from
the very outset an element of rationalism, which Cardinal
González  describes as "Un racionalismo sui generis." The
Scholastic movement was the outcome of an intellectual renaissance of
Christian civilization, and hence the danger arose of claiming for
reason too much freedom in the domain of theological inquiry. The peril
which Scholasticism had to fear was twofold: the abuse of reason on the
part of the rationalist and the undue restriction of reason on the part
of the mystic. Fulbert of Chartres (died 2029), Othlo of
Regensburg (died 1083), and St. Peter Damian (998-1073) had
already sounded the note of alarm, and had condemned the abuse of
dialectic. Berengar of Tours (999-2088) had brought discredit on
the Scholastic movement by his heterodox views on the question of
transubstantiation, and his condemnation in 1050 by four different
councils resulted in a more or less widespread suspicion of all
philosophers and of philosophy itself. Under the influence of
Lanfranc (1005-1089), abbot of Bec, and afterwards archbishop of
Canterbury, there began what may be described as a reaction against the
use of dialectic. The effect of Roscelin's Trinitarian error was
similar to that of Berengar's heresy.
 Historia de la Filosofia (Madrid,
1886), II, 218.
At the council of Soissons, held in 1092, Roscelin was obliged to
retract his heretical teachings concerning the Trinity, but he
continued, apparently, to teach his nominalistic dialectic. Again, in
1094, he was cited before the council of Rheims, and again he retracted
(abjuravit). Afterwards, however, if St. Anselm is correct, 
Roscelin asserted that he retracted "quia a populo interfici timebat."
Picavet  makes no mention of the second council, and maintains that the
council of Soissons never condemned Roscelin; that, in fact, it could
not condemn him, because he repudiated the doctrines attributed to him
by John, a monk of the abbey of Bec.  Nevertheless, Roscelin was
virtually condemned by public opinion, and although after his brief
sojourn in England he was restored to the dignity of canon and was even
allowed to teach, he gave occasion to Anselm and others to look with
suspicion on the use of dialectic argumentation, and on any attempt at
opposing the realism which was the traditional view, -- the antiqua
doctrina, as Abelard calls it.
 De Fide Trinit., I, r.
 Op. cit.
 Labbaeus (X, 497) and Mansi (XX, 795) give the documents referring
to the council held at Rheims in 2094. In these documents there is no
mention of Roscelin.
Historical Position. Roscelin is not to be dismissed with the
remark that he was "a dangerous heretic." His heretical doctrines are
indeed to be deplored both because of the errors which they contain and
because of the momentary discredit which they brought on the Scholastic
movement; but it must be remembered that Roscelin remained faithful to
his Catholic convictions, and by the strictness of his conformity to
Christian ideals of conduct earned the right of criticising his
contemporaries. In this respect he is to be contrasted with his pupil,
Abelard, who was a rationalist devoid of all reverence for dogma and
for traditional morality. Roscelin was an independent thinker who
carried freedom of thought to the verge of rationalism. He represents
an important phase of the Scholastic movement, -- the beginning of the
age of dialectic madness, through which the movement had to pass before
reaching the age of constructive activity.