Little is known of his life. He seems to have taught in the schools of Paris, and he attended the Lateran Council in 1179. He afterwards inhabited Montpellier (he is sometimes called Alanus de Montepessulano), lived for a time outside the walls of any cloister, and finally retired to Citeaux, where he died in 1202.
He had a very widespread reputation during his lifetime and his knowledge, more varied than profound, caused him to be called Doctor universalis. Among his very numerous works two poems entitle him to a distinguished place in the Latin literature of the Middle Ages; one of these, the De planctu naturae, is an ingenious satire on the vices of humanity. He created the allegory of grammatical "conjugation" which was to have its successors throughout the Middle Ages. The Anticlaudianus, a treatise on morals as allegory, the form of which recalls the pamphlet of Claudian against Rufinus, is agreeably versified and relatively pure in its latinity.
As a theologian Alain de Lille shared in the mystic reaction of the second half of the 12th century against the scholastic philosophy. His mysticism, however, is far from being as absolute as that of the Victorines. In the Anticlaudianus he sums up as follows: Reason, guided by prudence, can unaided discover most of the truths of the physical order; for the apprehension of religious truths it must trust to faith. This rule is completed in his treatise, Ars catholicae fidei, as follows: Theology itself may be demonstrated by reason. Alain even ventures an immediate application of this principle, and tries to prove geometrically the dogmas defined in the Creed. This bold attempt is entirely factitious and verbal, and it is only his employment of various terms not generally used in such a connection (axiom, theorem, corollary, etc.) that gives his treatise its apparent originality.
Alain de Lille has often been confounded with other persons named Alain, in particular with another Alanus (Alain, bishop of Auxerre), Alan, abbot of Tewkesbury, Alain de Podio, etc. Certain facts of their lives have been attributed to him, as well as some of their works: thus the Life of St Bernard should be ascribed to Alain of Auxerre and the Commentary upon Merlin to Alan of Tewkesbury. Alan of Lille was not the author of a Memoriale rerum difficilium, published under his name, nor of Moralium dogma philosophorum, nor of the satirical Apocalypse of Golias once attributed to him; and it is exceedingly doubtful whether the Dicta Alani de lapide philosophico really issued from his pen. On the other hand, it now seems practically demonstrated that Alain de Lille was the author of the Ars catholicae fidei and the treatise Contra haereticos.
In his sermons on capital sins, Alain argued that sodomy and homicide are the most serious sins, since they call forth the wrath of God, which led to the destruction of Sodom and Gomorrah. His chief work on penance, the Liber poenitenitalis dedicated to Henry de Sully, exercised great influence on the many manuals of penance produced as a result of the Fourth Lateran Council. Alain's identification of the sins against nature included bestiality, masturbation, oral and anal intercourse, incest, adultery and rape. In addition to his battle against moral decay, Alan wrote a work against Islam, Judaism and Christian heretics dedicated to William VIII of Montpellier.
• God is an intelligible sphere whose centre is everywhere and whose circumference is nowhere.
• Do not hold as gold all that shines as gold.