The revival of the principles of mysticism was a natural result of the
decadent condition of philosophy during the fourteenth and fifteenth
centuries. The heaping of subtlety on subtlety and the interminable
controversies of the advocates of Thomism and Scotism bewildered and
disgusted the serious seeker after spiritual light and drove him
eventually to abandon all intellectual philosophy in favor of a life of
contemplation and prayer. Many believed with the author of the
Imitation of Christ that it is better to feel contrition than to
know its definition, and that he is very learned indeed who does the
will of God and renounces his own will. However, the condemnation of
philosophy by the mystics reacted on the mystics themselves. Being
unwilling to enter into the disputes of the schools, and obeying to the
letter their resolve to abstain from philosophical speculation, they
were unable to detect error when it was introduced into their own
school. They judged all philosophy by the decadent systems which then
flourished, and in their depreciation of purely rational speculation
they overlooked the fact that without the safeguard of systematic dogma
mysticism is unable to resist the inroads of pantheism and other
errors. Thus it happened that the first mystics, who drew from the pure
Christian sources, were soon followed by others, who drew from sources
tainted with the pantheism of the Averroists. We must distinguish,
therefore, the orthodox mystics and the heterodox mystics.
Orthodox Mystics. John Ruysbroek (1293-1381) may be regarded as
the founder of the orthodox mysticism of this period. After having been
chaplain at St. Gudule, in Brussels, he retired to the convent of the
Augustinians at Groenendael, where he gave himself to the study and
practice of asceticism. Through Gerhard Groot (1340-1384), the
founder of the Brothers of the Common Life, the influence of Ruysbroek reached the members of
the community at Deventer, among whom was Thomas Hemerken or
à Kempis (1380-1471),  the author of the Imitation of
 Fifteenth century writers, including Thomas himself (cf.Opera, ed. 1576, Vol. I, pp. 453 ff.), refer to the order as
Canonici Regulares Sancti Augustini, vulgo dicti Fratres. It was
Florentius, successor of Gerhard Groot, who founded the community at
Agnetenberg, near Zwolle, where Thomas spent the greater part of his
life. A recent work on Thomas à Kempis is Scully's Life of
Venerable Thomas à Kempis (London, 1901).
Life. The most influential of the orthodox mystics of the
fourteenth and fifteenth centuries was John Gerson, Doctor
Christianissimus. He was born at Gerson, in the diocese of Rheims,
about the year 1364. After having studied under Peter d'Ailly in the
Faculty of Arts at Paris, he entered the department of theology, and in
1395 became chancellor of the university. In 1397 he went to Bruges,
where he made the acquaintance of the Flemish exponents of mysticism.
In 1401 he returned to Paris, but about the year 1419 was obliged to
retire from the university for having advocated the cause of the
opponents of papal authority. He entered the monastery of the
Celestines at Lyons, and there devoted himself to prayer and study. He
died in the year 1429. His works, which were published in 1483, include
De Theologia Mystica Speculativa, De Theologia Mystica Practica, De
Elucidatione Scholastica Mysticae Theologiae, and many other
treatises on philosophy, theology, and canon law.
Gerson was opposed equally to the formalism of the Scotists and to the
terminism of the Ockamists. Indeed, he was opposed to all philosophy
except in so far as philosophy is seasoned with piety. In a sermon,
Omnibus Sanctis, he condemns those self-dubbed philosophers who
separate philosophy from the practice of religion, "qui se dici
philosophos volunt, et non sunt, quoniam dum a religione secernere
putant philosophiam, utramque perdunt."  In the treatise De Mystica
Theologia Speculativa he describes contemplative ecstasy after the manner and almost in the
words of his favorite author, St. Bonaventure: "Est igitur extasis
raptus mentis cum cessatione omnium operationum in inferioribus
 Opera (The Hague edition, 1718), Vol. III, col. 1517.
 Op. cit., Vol. III, col. 391.
DENIS THE CARTHUSIAN
Life. Denis the Carthusian, Doctor Ecstaticus, was
born at Ryckel, in the Belgian province of Limbourg, in 1402. After
having obtained the degree of Master of Arts at Cologne, he entered the
Carthusian monastery at Roermonde. He died in 1471. A complete edition
of the works of the Carthusian is being published by the monks of Notre
Dame des Prés. The eighteenth volume appeared in 1899.
 Cf. De Wulf, Hist. de la phil, méd., p. 370;
also Mougel, Dionysius der Karthäuser (Mulheim, 1898), and
American Ecclesiastical Review, November, 1899.
Denis carefully avoids entering into the subtleties of the
controversies which were agitating the schools in his day.
"Impertinentes subtilitates vitare propono."  In the main his system
of philosophy and theology is Thomistic. He considers, however, all
speculative knowledge to be merely an introduction to the interior life
of contemplation and ecstasy. In the mystic elements of his system he
draws largely from the Pseudo-Dionysius.
 Commentarius in Psalmos, Prooem.
Heterodox Mystics. The Averroism which prevailed during the
fourteenth and fifteenth centuries, whether openly professed as it was
by John of Gand (or John of Jandun, erroneously called
John of Ghent), or taught more covertly as it was in different forms by
John De Mirecourt and Guido  of Medonta, took the form of an
anti-Scholastic movement tending towards a revival of the pantheism of
the twelfth century. A similar tendency towards pantheism led some of
the mystics of this time to maintain the identity of the creature with the Creator in the
act of contemplative ecstasy -- a doctrine which was repudiated by
orthodox mystics. Some of the first heterodox mystics, such as Eckhart,
show little or no trace of Averroistic influence; it was on the
societies or brotherhoods of mystics that the Averroists brought their
pantheistic doctrines to bear, thus widening the gulf between true and
 AEgidius de Medonta; cf.Chartul., III, 23.
Master Eckhart  (or Eckhardt) was born about the year 1260. He
studied first at Cologne, and afterwards at Paris. He belonged to the
order of St. Dominic. In 1326 the archbishop of Cologne instituted
proceedings against Eckhart, who was then teaching in the convent of
his order at Cologne. Eckhart repelled the charge of heresy, and in
1327 appealed to the Holy See. He died in 1327. In 1329 twenty-eight
propositions taken from his writings were condemned by John XXII. 
 Cf. Denifle, in Archiv f. Litteratur u. Kirchengesch. d.
Mittelalters, 1886; Jundt, Hist. du panthéisme au Moyen
Age, pp. 231 ff.; and Denzinger, Enchiridion, Ed. VII, propp.
 Chartul., II, 322.
In his Latin work entitled Opus Tripartitum, and in his sermons,
written in German, Eckhart advocated a system of mysticism in which he
maintained the disappearance of all distinction between the Creator and
the creature in the act of contemplation. He taught that the supreme
happiness of man consists in a deification by which man becomes one
with God. 
 Cf. Denzinger, op. cit., prop. 437.
Henry Suso (died 1366) and John Tauler (1290-1361), who
were influenced by Eckhart's mystic doctrines, prepared the way for the
Protestant mysticism of Sebastian Franck (1500-1545),
Valentine Weigel (1533-1588), and Jakob Böhme
(1575-1624), which, together with the cabalistic mysticism of John
Reuchlin (1455-1522), flourished in the Renaissance period.