From the Christian History Institute (quoted in Abu Daoud's post) comes this about Raymund's conversion:
Raymond Lull would have seemed an unlikely person to remind the church of its missionary vision. A court gallant (that is, a fashionable ladies' man) and poet, he squandered his life in frivolity, romantic stories, love poems, and seduction. He was thirty before that changed.
But Jesus Christ, of his great clemency,
Five times upon the cross appeared to me,
That I might think upon him lovingly,
And cause his name proclaimed abroad to be...
It is reported that Lull's conversion was precipitated by a shock. He tried to lure a beautiful woman into a few moments of pleasure in bed with him. With quiet dignity, the woman revealed her breast to him--cancer-eaten. In a flash, he saw the futility of his lusts, and later transferred his love to the eternal Christ.
From the Catholic Encyclopedia:
From that time he seemed to be inspired with extraordinary zeal for the conversion of the Mohammedan world. To this end he advocated the study of Oriental languages and the refutation of Arabian philosophy, especially that of Averroes. He founded a school for the members of his community in Majorca, where special attention was given to Arabic and Chaldean. Later he taught in Paris. About 1291 he went to Tunis, preached to the Saracens, disputed with them in philosophy, and after another brief sojourn in Paris, returned to the East as a missionary. After undergoing many hardships and privations he returned to Europe in 1311 for the purpose of laying before the Council of Vienna his plans for the conversion of the Moors. Again in 1315 he set out for Tunis, where he was stoned to death by the Saracens.Despite his life of missionary activity and martyrdom, Raymund Lully was never declared a saint because of his belief that philosophy and theology were identical, a belief that was eventually condemned (sixty years after his death) by Pope Gregory XI. However his life of missionary activity is certainly admirable, and his work on a medieval logical engine sounds like the sort of thing that Umberto Eco would thrive on.
Raymond's literary activity was inspired by the same purpose as his missionary and educational efforts. In the numerous writings (about 300) which came from his facile pen, in Catalonian as well as in Latin, he strove to show the errors of Averroism and to expound Christian theology in such a manner that the Saracens themselves could not fail to see the truth. With the same purpose in view, he invented a mechanical contrivance, a logical machine, in which the subjects and predicates of theological propositions were arranged in circles, squares, triangles, and other geometrical figures, so that by moving a lever, turning a crank, or causing a wheel to revolve, the propositions would arrange themselves in the affirmative or negative and thus prove themselves to be true. This device he called the Ars Generalis Ultima or the Ars Magna, and to the description and explanation of it he devoted his most important works. Underlying this scheme was a theoretical philosophy, or rather a theosophy, for the essential element in Raymond's method was the identification of theology with philosophy. The scholastics of the thirteenth century maintained that, while the two sciences agree, so that what is true in philosophy cannot be false in theology, or vice versa, they are, nevertheless, two distinct sciences, differing especially in that theology makes use of revelation as a source, while philosophy relies on reason alone.
The Arabians had completely separated them by maintaining the twofold standard of truth, according to which what is false in philosophy may be true in theology. Raymond, carried on by his zeal for the refutation of the Arabians, went to the opposite extreme. He held that there is no distinction between philosophy and theology, between reason and faith, so that even the highest mysteries may be proved by means of logical demonstration and the us of the Ars Magna. This of course removed all distinction between natural and supernatural truth. Unlike Abelard's, however, Raymond's rationalism was of the mystic type: he taught expressly that, for the understanding of the highest truths, reason must be aided by faith; that once faith has flooded the soul with its radiance, reason, enlightened and strengthened by faith, "is as capable of showing that there are three persons in one God as it is of proving that there cannot be three Gods".