During the twelfth century Chartres became the scene of a Platonic
reaction against the anti-realism represented by Roscelin and Abelard.
The founders of the school of Chartres were the brothers Bernard
and Theodoric of Chartres, with whom were associated William
of Conches and Gilbert de la Porrée. 
 On the school of Chartres, cf. Clerval, Les écoles
de Chartres au Moyen-Âge (Chartres, 1895).
BERNARD OF CHARTRES
Life. Bernard of Chartres taught at Chartres during the early
part of the twelfth century. Among his disciples were William of
Conches and Gilbert de la Porrée. In 1119 he was made
chancellor of the church of Chartres. He died about the year 1125.
Sources. According to John of Salisbury, Bernard composed a
prose treatise, De Exositione Porphyrii, a metrical treatise on
the same subject, a moral poem on education, and probably a fourth work
in which he sought to reconcile Plato with Aristotle. Fragments of
these treatises are to be found in the Metalogicus, IV, 35, and the Polycraticus,
VII, 3 (apud Migne, Patr. Lat., Vol. CXLIX, coll. 938 and 666).
Hauréau op. cit., I, 408) falls into the common error of
confounding Bernard of Chartres with Bernard of Tours, and assigns to
the former works which are to be ascribed to the latter.
Bernard, in common with others of his school, devoted more attention to
the study of the Timaeus and of the works of the Neo-Platonists
than to the study of Aristotle's dialectical treatises and of the
commentaries of Boethius. Consequently, he not only discussed the
problem of universals (distinguishing between the abstract, the
process, and the concrete, -- albedao, albet, and
album),  but also occupied himself with problems of
metaphysics and cosmology.
 Cf.Metal., III, 2, apud Migne, Patr.
Lat., Vol. CXCIX, col. 893.
Metaphysics. There are three categories of reality, -- God,
matter, and idea. God is supreme reality. Matter was brought out of
nothingness by God's creative act, and is the element which, in union
with Ideas, constitutes the world of sensible things. Ideas are the
prototypes by means of which the world was from all eternity present to
the Divine Mind; they constitute the world of Providence ("in qua omnia
semel et simul fecit Deus"), and are eternal but not coeternal with
God. According to John of Salisbury, Bernard also taught that there
exist native forms -- copies of the Ideas created with matter -- which
are alone united with matter. It is difficult, however, to determine
what was Bernard's doctrine on this point. It is sufficient to note
that he reproduced in his metaphysical doctrines many of the
characteristic traits of Platonism and Neo-Platonism, -- the intellect
as the habitat of Ideas, the world-soul, eternal matter, matter
the source of imperfection, etc.
Cosmology. Matter, although caused by God, existed from all
eternity. In the beginning, before its union with the Ideas,
it was in a chaotic condition. It was by means of the native forms,
which penetrate matter, that distinction, order, regularity, and number
were introduced into the universe.
THEODORIC OF CHARTRES
Life. Theodoric of Chartres was magister scholae at
Chartres about the year 1121. It is said that he taught at Paris in the
year 1140: it was probably at Paris that he taught rhetoric to John of
Salisbury. In we find Theodoric teaching once more at Chartres. Like
Bernard, he devoted more attention to the study of the Platonists than
to that of the Aristotelians. The most probable date of his death is
Sources. Besides the work De Sex Dierum Operibus, of
which a mutilated manuscript copy has come down to us, Theodoric wrote
a commentary on the De Inventione Rhetorica ad Herennium. This
commentary, which was first published in 1884, is an indication of the
humanistic tendency of the school of Chartres. 
 The work De Sex Dierum Operibus was published by
Hauréau (Notices, etc., Vol. XXXII, Part II, p. 167);
Clerval (op. cit., p. 172) mentions a work entitled
Theodoric was an enthusiastic student of the classics, "artium
studiosissimus investigator," as John of Salisbury says. We know that
he possessed a Latin translation of the Planisphere of Ptolemy,
which he obtained from the Arabian scholars of Toulouse. It was,
however, to the Platonic metaphysics and cosmology that he devoted his
attention as a philosopher, taking his stand with the other
"Chartrains" on the side of the Platonic realists.
Metaphysics. Going farther in his advocacy of Neo-Platonic
principles than Bernard had gone, identifying unity with divinity and
divinity with reality, Theodoric maintained the principles "Divinitas
singulis rebus forma essendi est" and "Omne quod est ideo est quia unum
est."  Now, if divinity is synonymous with reality and is the
intrinsic essential principle of all things,
Theodoric's system is fully developed pantheism. Quite recently,
however, Baeumker has shown  that here, as in the case of Eckart and
other mediaeval mystics, we must distinguish between the individual
essence, which is proper to each created being, and the formal
essence, the divine in each creature, which is God. Technically,
therefore, Theodoric must be considered innocent of the charge of
teaching explicit pantheism.
 Cf. Hauréau, loc. cit. and Clerval, op.
cit., pp. 255 ff.
 Cf.Archiv f. Gesch. der Phil., X, 138.
Cosmology. In the work De Sex Dierum Operibus Theodoric
set himself the task of showing that the Neo-Platonic account of the
origin of the universe agrees with the Mosaic account of the creation.
Moses, he declared, was prudeniissimus philosophorum.
WILLIAM OF CONCHES
Life. William of Conches, a pupil of Bernard of Chartres, after
having taught a system of Platonic realism in the schools at Paris
(about 1122), was warned by William of St. Thierry that his
theological doctrines, and in particular his apparent identification of
the Holy Ghost with the world-soul, would lead to heresy. Thereupon he
abandoned the study of theology and, seeking the protection of Geoffrey
the Fair, count of Anjou, devoted himself to the study of nature.
William is the first of the mediaeval philosophers to show acquaintance
with the physical science of the Arabians, which, through the
translations made by Constantine the African, began to be known in
Europe about the middle of the twelfth century.
Sources. No question of mediaeval bibliography is more
hopelessly intricate than that of the authorship of the works
attributed to William of Conches. The most recent investigations and
discussions  seem to warrant the following list: glosses on the
Timaeus, a commentary on Boethius' De Consolatione
Philosophiae, a treatise De Philosophia, of which the
Dragmaticon (probably Dramaticon) is a corrected edition
cast in dialogue form, and the Magna de Naturis Philosophia. It
is almost certain, however, that the last mentioned work, of which no
copy is extant, belongs to a later date and was written by William of
Auvergne. The Dragmaticon in its earliest form is published by
Migne (Patr. Lat., Vol. XC, coll. 2227 ff.), under the title
Elementorum Philosophia. Libri Quatuor.
 Cf. Poole, Illustrations of the History of Medieval
Thought (London, 1884), pp. 338 ff.
After his retirement from the field of theological and metaphysical
controversy, in which he had sustained the cause of the Platonists, who
were edging closer and closer to the border line of pantheism, William,
inspired by the labors of the Arabian physicists, took up the study of
psychology and cosmology.
Psychology. In his study of the processes of knowledge William
distinguishes between sensation, imagination, and reason. Rejecting the
theory of forms mediating between object and subject, he devotes his
attention to what we should call the physiological aspect of the
problems of psychology. There are, he says, three departments in the
brain ("in capite tres sunt cellae una in prora, altera in puppe,
tertia in medio "). In the front part of the brain is the region of
vision (fantastica), in the middle is the region of thought
(logistica), and in the rear portion is the region of memory
(memorialis). In his commentary on the Timaeus, however,
he speaks as a Platonist. Above all the faculties of the soul, he says,
is nous (intelligence), by which alone we are enabled to
perceive the incorporeal.
Cosmology. In his account of the universe and the elements which
compose it, our philosopher is an atomist: "Sunt, igitur, in
unoquoque corpore minima quae, simul juncta, unum magnum constituunt";
and when the interlocutor objects that this is the opinion of Epicurus,
William answers that there is no sect that has not some admixture of
 Cf.Dragmaticon, I, 25, quoted by Poole, op.
cit., p. 349.
GILBERT DE LA PORRÉE
Life. Gilbert was born at Poitiers, in 1076. He was successively
the pupil of Bernard of Chartres and of Anselm of Laon. After teaching
for about twenty years at Chartres, where he held the office of
chancellor, he went to Paris and there lectured on dialectic and
theology. Later on he returned to Poitiers, of which city he was made
bishop in 1142. On account of his theological doctrines concerning the Trinity and the
Incarnation he was suspected of heresy by St. Bernard and his
followers. The council of Paris, which, in 1147, was summoned to
consider his doctrines, and which was presided over by Eugenius III,
was unable to arrive at a decision. It reassembled at Rheims in the
following year. According to the account given by John of Salisbury,
who was present, and by Otto of Freising, also a contemporary, it was
not the doctrine of Gilbert but the influence of St. Bernard that was
on trial. The outcome seems to have been that the council decided
nothing. Gilbert returned to his see and was not further molested. He
died in 1154.
Sources. Gilbert composed a work entitled De Sex
Principiis , a treatise on the last six of the Aristotelian
categories. This book was made the basis of commentaries by Albert the
Great; it was frequently referred to by St. Thomas, and it was held in
great esteem as a text-book on logic until the close of the Middle
Ages. Gilbert wrote also a commentary on the treatise De
Trinitate, which was supposed to have been written by Boethius.
Mention is also made of a work De Duabus Naturis et Una Persona
Christi; this, however, is apparently the fourth book of the
pseudo-Boethian compilation. The commentary on the pseudo-Boethian
treatise is published by Migne, Patr. Lat., Vol. LXIV, and the
treatise De Sex Principiis, ibid., Vol. CLXXXVIII, coll. 1257
Notwithstanding the renown which Gilbert attained as an exponent of
Aristotelian dialectic, his philosophy, as far as we know it, breathes
the spirit of Plato and betrays the Platonizing influence of the school
Doctrine of Universals. In his doctrine of universals Gilbert,
according to John of Salisbury, attributed universality to the formae
nativae existing in things:
Est autem farina nativa originalis exemplum et quae non in mente Dei
consistit, sed rebus creatis inhaeret. Haec Graeco eloquio dicitur
 Metal., II, 27.
Nativa in the context evidently means new, born, created. But
what are these created forms inherent in created things? It is
usual to represent them as full-fledged universals, possessing their
universality antecedently to the act of the human mind; and if this
interpretation be correct, Gilbert should be reckoned among the
ultra-realists. It is evident, however, from the commentaries on the
Four Books on The Trinity, that Gilbert attached quite a
different meaning to the formae nativae. He says, for example:
Non solum enim rationalium sed etiam non rationalium substantiarum
individuarum universalia quaedam sunt, quae ab ipsis individuis humana
ratio quodammodo abstrahit ut earum naturam perspicere . . . possit. 
 Migne, Patr. Lat., Vol. LXIV, col. 1374.
It is, therefore, the mind that abstracts the universal and makes it to
be universal, -- a formula which at once separates Gilbert from the
ranks of the ultra-realists. Elsewhere  he bases the unity of the
universal on the similarity of essences, -- another formula which is
opposed to ultra-realism. There must, however, be some reason why so
many historians have counted Gilbert among the ultra-realists, and the
explanation may possibly be found in the fact that his general
metaphysical doctrines are Platonic.
 As e.g., col. 1263.
Metaphysical Doctrines. Thus, when Gilbert distinguishes between
the essential reality, which he calls the subsistence ("id quo
est"), and the individual determination, which he calls the
substance ("id quod est"), an Aristotelian might admit the
distinction. Gilbert, however, goes so far as to maintain that unity,
for example, is a subsistence distinct from that which is one.  The
Platonic tendency is also apparent in the doctrine of native forms,
although Gilbert is careful to avoid the Neo-Platonic doctrine that the
forms are in some sense to be identified with the mind of God ("non in
mente Dei consistit").
 Cf.op. cit., col. 1376.
Historical Position of the School of Chartres. The group of
philosophers included under the title of this chapter represents an
eclectic tendency, that is, an attempt at uniting Platonism
with Aristotelianism. To this eclectic tendency is joined a broader
spirit of humanism and, at least in the case of William of Conches, a
spirit of scientific inquiry. The spirit of eclecticism and also the
humanistic and scientific spirit are still more marked in the next
group of philosophers.