The Jews were at this period the principal representatives of the commerce of the world. While the nobles devoted themselves to the business of war, the commoners to trades, and the peasants and serfs to agriculture, the Jews, who were not liable to be called upon to perform military service, and possessed no feudal lands, turned their attention to the exportation and importation of goods and slaves, so that the favor extended to them by Charlemagne was, to a certain extent, a privilege accorded to a commercial company. They experienced only the restraint put upon all merchants in the corn and wine trade; the Emperor considered it dishonest to make a profit on the necessaries of life. This somewhat materialistic value set upon the Jews marks, however, great progress from the narrow-mindedness of the Merovingian monarchs, the Gunthrams and the Dagoberts, who saw nothing in the Jews but murderers of God. But Charlemagne also manifested deep interest in the spiritual advancement of the Jewish inhabitants of his empire. In the same way as he had cared for the education of the Germans and the French by inviting learned men from Italy, so also he earnestly desired to place a higher culture within the reach of the German and the French Jews. With this intention he removed a learned family, consisting of Kalonymos, his son Moses, and his nephew, from Lucca to Mayence (787), hoping besides to make the Jews independent of the academies of the Levant.
Charlemagne's embassy to the powerful Caliph Haroun Alrashid, to which was attached a Jew named Isaac, is familiar to every student of history (797). Although at first probably Isaac accompanied the two nobles, Landfried and Sigismund, only in the character of interpreter, he was nevertheless admitted into Charlemagne's diplomatic secrets. Thus, when the two principal ambassadors died on the journey, the Caliph's reply and the valuable presents which he had forwarded, fell into Isaac's sole charge, and he was received in solemn audience by the Emperor at Aix. The Emperor is also said to have requested the Caliph, through his embassy, to send him from Babylonia a learned Jew for his country, and Haroun is reported to have sent him a man answering his requirements. This man was a certain Machir, whom Charlemagne placed at the head of the Jewish congregation of Narbonne. Machir, who, like Kalonymos of Lucca, became the ancestor of a learned posterity, founded a Talmudical school at Narbonne.
Owing to their favorable position in the Frankish-German Empire, in which they held land, the Jews were permitted to undertake voyages and carry on business, and were harassed neither by the people nor by the really religious German ecclesiastics; they were also enabled to abandon themselves to their inclination for travel, and thus spread through many of the provinces of Germany. In the ninth century, numbers of them dwelt in the towns of Magdeburg, Merseburg, and Ratisbon. From these points, they penetrated further and further into the countries inhabited by the Slavonians on the further side of the Oder as far as Bohemia and Poland. Meanwhile, in spite of the favor which Charlemagne extended to them, he, like the best men of the Middle Ages, found it difficult to treat them on an entirely equal footing with the Christians. The chasm, which the Fathers of the Church had placed between Christianity and Judaism, and which had been widened by individual ecclesiastics and the synods, was far too deep to be overleapt by an emperor who was devotedly attached to the Church. Charlemagne himself maintained, on one point, a difference between Jew and Christian, and perpetuated it in the peculiar form of the oath which was imposed on the Jews who were witnesses against, or accusers of, a Christian. They were required, in taking an oath against a Christian, to surround themselves with thorns, to take the Torah in their right hand, and to call down upon themselves Naaman's leprosy and the punishment of Korah's faction in witness of the truth of their statement. If there was not a Hebrew copy of the Torah at hand, a Latin Bible was held to be sufficient. It is impossible not to admit, however, that to allow the Jews to testify against a Christian was in itself a deviation from the ordinances of the Church.
In the East, at the beginning of the ninth century, the Jews were also reminded, in a disagreeable manner, that they had to expect scorn and oppression even from the best rulers. The reigns of the Abassid Caliphs, Haroun Alrashid and his sons, are regarded as the most flourishing period of the Caliphate of the East, but it is at this very time that Jewish complaints of oppression rise loudest. It is possible that in re-enacting Omar's law against the Christians (807), Haroun also made it applicable to the Jews; for they were compelled to wear a distinctive badge of yellow on their dress, in the same way as the Christians were obliged to wear blue, and they had to use a rope instead of a girdle. When, after his death (809), his two sons, Mahomet Alemin and Abdallah Almamun, for whom their father had divided the Caliphate into two parts, engaged in a destructive civil war, throughout the whole extent of the great empire, the Jews, especially those in Palestine, experienced severe persecution. The Christians, however, were their companions in misfortune. During the four years (809–813) of this fratricidal struggle, robbery and massacre seem to have been the order of the day. The sufferings were so terrible, it seems, that a preacher of those times declared them to be a sign of the speedy coming of the Messiah. "Israel can only be redeemed by means of penitence, and true penitence can only be evoked by suffering, affliction, wandering, and want," declared this orator by way of consolation of his afflicted congregation. In the civil war raging between the two Caliphs, he fancied he saw the approaching destruction of the Ishmaelite rule and the approach of the Messianic empire. "Two brothers will finally rule over the Ishmaelites (Mahometans); there will then arise a descendant of David, and in the days of this king the Lord of Heaven will found a kingdom which shall never perish." "God will exterminate the sons of Esau (Byzantium), Israel's enemies, and also the sons of Ishmael, its adversaries." But these, like many others, were delusive hopes. The civil war, indeed, shook the Caliphate to its foundations, but did not destroy it. Alemin was killed, and Almamun became the sole ruler of this extensive empire.
It was during Almamun's reign (813–833) that the Caliphate of the East flourished most luxuriantly. As he was imbued with tolerance, it was possible for the sciences and a certain form of philosophy to develop. Bagdad, Kairuan in northern Africa, and Merv in Khorasan, became the centers of science, such as Europe did not possess until many centuries later. The genius of the Greeks celebrated its resurrection in Arabic garb. Statesmen competed with men of leisure for the palm of erudition. The Jews did not remain unaffected by this enthusiasm for science. Investigation and subtle inquiry are indeed part of their innermost nature. They took earnest interest in these intellectual activities, and many of their achievements gained the approbation of the Arabs. The history of Arab civilization has several Jewish names recorded in its annals. Sahal, surnamed Rabban (the Rabbanite, the authority on the Talmud), of Taberistan on the Caspian Sea (about the year 800), was celebrated as a physician and a mathematician. He translated into Arabic the Almagest of the Greek astronomer Ptolemy, the text-book of astronomy during the Middle Ages, and was the first to note the refraction of light. His son Abu-Sahal Ali (835–853) is placed among those that advanced the study of medicine, and was the teacher of two Arabic medical authorities, Razi and Anzarbi.
With even more ardor than that with which they had applied themselves to medicine, mathematics and astronomy, the Mussulmans prosecuted the study of the science of religion, a sort of philosophy of religion (Kalâm). It was invested with as much importance as the affairs of state, and exercised a certain influence on politics. The expounders of the Koran, in trying to explain away the grossly sensual references to God, and to reconcile the contradictions contained in that work, developed ideas which projected far beyond the restricted horizon of Islam. Many commentators, by reason of their rationalistic explanations, came into conflict with the champions of the text, and were branded by them as heretics. The Mutazilists (heretics) laid great stress upon the unity of God, and desired that no definite attributes should be ascribed to him; for thereby the essence of God appeared to them to be divided into parts, and several beings to be included in the idea of God, whose unity was thus negatived. They further asserted the freedom of the human will, because the unconditional predetermination by God, which the Oriental mind believes, and the Koran confirms, was incompatible with divine justice, which rewards the good and punishes the bad. They believed, however, that they still stood on the same ground as the Koran, although, of course, going far beyond it, and in order to bring their doctrine into harmony with the blunt sayings of their religious book, they employed the same method as the Alexandrian-Jewish philosophers of religion had used to reconcile the Bible with Greek philosophy; they adopted an allegorical interpretation of the text. This interpretation was employed for the purpose of bridging over the gulf existing between the rationalistic idea of God and the irrational idea as taught by the Koran. The rationalistic Mutazilist theology of the Mahometans, although denounced at first as heretical, steadily gained ascendancy; the schools of Bagdad and Bassora rang with its doctrines. The Caliph Almamun exalted it into the theology of the court, and condemned the old simple views of religion.
The adherents of orthodoxy were horrified by this license of interpretation, for the text of the Koran, in an underhand way, was forced into conveying an opposite meaning, and simple faith lost all support. They, therefore, adhered strictly to the letter and to the natural meaning of the text. Some of them went still further. They took, in their literal meaning, all the expressions concerning God, however gross they might be, which occurred in the Koran, or were used by tradition, and constructed a most vile theology. Mahomet expressed a revelation thus: "My Lord came to meet me, gave me his hand in greeting, looked into my face, laid his hand between my shoulders, so that I felt his cold finger-tips," and the orthodox school accepted all this in revolting literalness. This school (Anthropomorphists) did not hesitate to declare that God was a body possessed of members and a definite form; that he was seven spans high, measured by his own span; that he was in a particular spot – upon his throne; that it was permissible to affirm of him that he moves, mounts his throne and descends from it, stops and rests. These and still more blasphemous descriptions of the Supreme Being, in the same grossly materialistic strain, were given by the orthodox Mahometan teachers of religion, in order to show their adherence to the letter of the Koran in contradistinction to the Rationalists.
The Jews of the East lived in so close a connection with the Mussulmans that they could not fail to be affected by these tendencies. The same phenomena were repeated, therefore, in Jewish circles, and the variance between Karaites and Rabbanites assisted in transferring the Islamic controversies to Judaism. The official supporters of Judaism, however, the colleges of Sora and Pumbeditha, held aloof from them. Entirely absorbed in the Talmud, and its exposition, they either took no notice at first of the violent agitation of mind prevailing, or else refused to yield to it. But outside of the colleges men were actively interested in these new methods, and Judaism was pushed through another process of purification.
The faint ray of philosophy which fell into this world of simple blind faith, ignorant of its own beliefs, produced a dazzling illumination. The Karaites for the most part were of Mutazilist (rationalistic) tendency, while the Rabbanites, on the contrary, having to defend the strange Agadic statements concerning God, were antagonistic to science. But as the religious edifice of Karaism was not finished, there arose new sects within its pale, with peculiar theories and varying religious practices.
The first person known to have imparted the Mutazilist tendency of Islamic theology to Judaism was Judah Judghan, the Persian, of the town of Hamadan (about 800). His adversaries relate of him that he was originally a camel-herd. He himself pretended to be the herald of the Messiah, and when he had gained adherents, unfolded to them a peculiar doctrine, which he asserted had been made known to him in a vision.
In opposition to the ancient traditional views, in accordance with which the Biblical account of God's deeds and thoughts must be taken literally, Judah Judghan asserted that we ought not to represent God with material attributes or anthropomorphically, for he is elevated above all created things. The expressions which the Torah employs in this connection are to be taken in a wholly metaphorical sense. Nor may we take for granted that, by virtue of His omnipotence and omniscience, God predetermines the acts of man. Much rather ought we to proceed from God's justice, and assume that man is master of his actions, and possessed of free will, and that reward and punishment are meted out to us according to our merit. While Judah of Hamadan was possessed of liberal views concerning theoretical questions, he recommended the severest asceticism in practice. His adherents abstained from meat and wine, fasted and prayed frequently, but were less strict with respect to the festivals. His followers, who long maintained themselves as a peculiar sect under the name of Judghanites, believed so firmly in him that they asserted that he was not dead, but would appear again, in order to bring a new doctrine with him, as the Shiites believed of Ali. One of his disciples, named Mushka, was desirous of imposing the doctrine of his master on the Jews by force. He marched out of Hamadan with a troop of comrades of similar sentiments, but, together with nineteen of his followers, was killed, in the neighborhood of Koom (east of Hamadan, southwest of Teheran), most probably by the Mussulmans.
Judah Judghan attached more importance to an ascetic mode of living than to the establishing of the philosophical basis of Judaism, and was therefore rather the founder of a sect than a religious philosopher. A contemporary Karaite, Benjamin ben Moses of Nahavend (about 800–820), spread the Mutazilist philosophy among the Karaites. Benjamin Nahavendi is regarded by his fellow-Karaites as an authority, and is honored by them as greatly as Anan, their founder, although he differed from the latter on many points. Benjamin was entirely permeated with the conceptions of the Mutazilists. He was scandalized, not only by the physical and human characteristics of God contained in the Scripture, but also by the revelation and the creation. He could not rest satisfied with the idea that the spiritual Being had created this earthly world, had come into contact with it, had circumscribed himself in space for the purpose of the revelation on Sinai, and uttered articulate sounds. In order not to abandon his elevated idea of God, and at the same time to preserve the revelation of the Torah, he adopted the following notion, as others had done before him: God had himself created only the spiritual world and the angels; the terrestrial universe, on the other hand, had been created by the angels, so that God ought to be regarded only as the mediate creator of the world. In the same way the revelation, the giving of the Law on Sinai, and the inspiration of the prophets were all the work of an angel only. Certain disciples adopted Benjamin's views, and formed a peculiar sect, called (it is not known for what reason) the Makariyites or Maghariyites.
While Benjamin Nahavendi, as is generally acknowledged, deviated widely from the Jewish system with respect to religious philosophy, he approached the Rabbanites on the subject of morals; he adopted many Talmudical ordinances, and left it to the free choice of the Karaites to reject or adopt them as their standard. In order to enforce obedience to the laws, Benjamin Nahavendi introduced a species of excommunication, which differed only slightly from the excommunication of the Rabbanites. When an accused person refused to obey the summons served on him, and attempted to evade judgment, he was to be cursed on each of seven successive days, and then excommunication pronounced on him. The excommunication consisted in the prohibition of intercourse with all the members of the community, who also were forbidden to greet him, or to accept anything from him; he was to be treated in all respects like one deceased, until he submitted. If he obstinately disregarded the decree, it was lawful to hand him over to temporal justice. Although Benjamin Nahavendi inclined to Rabbanism on certain points, he adhered firmly, nevertheless, to the Karaite principle of unrestrained research in the Bible. One ought not to tie one's self down to the authorities, but to follow one's own conviction; the son may differ from the father, the disciple from the master, as soon as they have reasons for their different views. "Inquiry is a duty, and errors occasioned by inquiry do not constitute a sin."
In the same manner as the orthodox Mahometan teachers of religion worked counter to the unrestrained subtlety of the Mutazilists, and, falling into the opposite extreme, conceived the divinity as possessed of a bodily form, so also did the Jewish adherents of the orthodox doctrine go astray, and, regarding the rationalistic innovation as a defection from Judaism, they conceived the most absurd ideas concerning the materiality of God. They even desired to accept in their most literal sense the Biblical expressions, "God's hand, God's foot, his sitting down, or walking about." The Agadic exposition of the Scripture, which occasionally made use of material, tangible figures, adapted to the comprehension of the people, promoted the acceptance of this anti-Jewish theory. This theory, the creation of an imbecile, gained adherents by reason of its mysterious nature. It gives a minute, corporeal description of the Deity, measures his height from head to foot by the parasang-scale, speaks in blasphemous detail of God's right and left eye, of his upper and lower lip, of his beard and of other members, which it would be sacrilegious even to mention. In order, however, not to prejudice the sublimity and majesty of God, this theory enlarges each organ to enormous proportions, and considers that justice has been done to the case when it adds that the scale by which the members are measured considerably exceeds the whole world (Shiur-Komah). To this God, whom it thus dissected and measured, the theory assigned a special house in heaven with seven halls (Hechaloth). In the uppermost hall, God is seated upon an elevated throne, the proportions of which are measured by the same enormous scale. The halls are populated by this materialistic theory with myriads of angels, to some of whom are assigned names formed by the arbitrary combination of Hebrew and foreign words into barbarous sounds. The chief angel, however, is a certain Metatoron, and the theory adds, after the example of the Christian and Mahometan authors, that he was Enoch or Henoch, originally a man, but transported by God into heaven, and converted into flames of fire. With evident pleasure the theory dwells upon the description of this abortion of a morbid fancy. It even dared place him at the side of the Divinity, and call him the "little God."
This theory, which was a compound of misunderstood Agadas, and of Jewish, Christian, and Mahometan fantastic notions, clothed itself in mysterious obscurity, and pretended to be a revelation. In order to answer the inquiry whence it had acquired this wisdom which enabled it to scoff at Judaism, in other words, at the Bible and the Talmud, it quotes alleged divine instructions. As there is no nonsense, however apparent, which cannot find adherents when earnestly and impressively enunciated, this doctrine of mystery, which was based upon a grossly material conception of God, found many followers. Its adepts called themselves "Men of Faith." They boasted of possessing the means of obtaining a view of the divine household. By virtue of certain incantations, invocations of the names of God and the angels, and the recitation of certain prayer-like chants, combined with fasting and an ascetic mode of living, they pretended to be able to perform supernatural deeds. For this purpose they made use of amulets and cameos (Kameoth), and wrote upon them the names of God or the angels with certain signs. Miracle-working was a trifle to these mystics. They asserted that every pious man had the power of performing miracles, if he only employed the proper means. To this end they wrote a number of works on the theory and practice of the esoteric doctrine; for the most part they contained downright nonsense, but here and there they rose to poetry. But this mystical literature only gave hints; the adepts would surrender the real key to a knowledge of the divine secrets and to the power of performing miracles only to certain persons, in whose hand and forehead they pretended to discover lines that proved them to be worthy of this favor.
This mystical doctrine flourished chiefly in Palestine, where the real study of the Talmud was languishing; little by little it made its way into Babylonia. This became apparent on the occasion of the election of a principal of the Pumbeditha academy (814). The best claim to this office was that advanced by a certain Mar-Aaron (ben Samuel), by reason of his erudition and on account of his having acted up till then as chief judge. Nevertheless, preference was given to the claim of a rival, the aged Joseph bar Abba, who was far inferior to him in learning; the reason of this preference being that the latter was an adept in mysticism, and was believed to be favored with the intimacy of the prophet Elijah. One day when this same Joseph bar Abba was presiding at a public meeting, he exclaimed with rapture, "Make room for the old man who is just coming in." The eyes of all present were immediately turned to the entrance, and those to the right of the principal respectfully stepped aside. They saw no one enter, however, and were therefore all the more positively convinced that the prophet Elijah had entered invisible, had seated himself on the right of his friend Joseph, and had been present during the whole of his discourse. After that time no one dared occupy the place at the side of the principal of the Pumbeditha academy, for it had been honored and hallowed by Elijah, and it became the custom to leave it vacant.
Joseph's successor, Mar-Abraham ben Sherira (816–828), was likewise a mystic. It was said that he could foresee the future from the rustling of palm leaves on a calm day.
More liberal views, and even Karaism, found a way into the halls of learning, just as mysticism had done before. Through these opposed views quarrels naturally arose, which came to light when the office of Exilarch was to be filled. In the year 825 there was to be the election of a new Prince of the Exile. For this office there were two candidates, David ben Judah and Daniel. The latter was inclined to Karaism, and perhaps just on this account found in southern Babylonia many supporters who gave him their votes. The Babylonians in the north, who belonged to Pumbeditha (Anbar), decided in favor of David, as he doubtless belonged to the orthodox party. The quarrel was carried on with much virulence. The mystic Abraham ben Sherira was deposed in consequence, and Joseph ben Chiya appointed in his place. It is not known by which party this was brought about. But Abraham had followers in Pumbeditha, who gave him their support, and refused allegiance to the rival Gaon. The quarrel could not be decided by their own authorities, and both parties appealed to the Caliph Almamun to confirm the Exilarch of their choice. Almamun, however, at that time was engaged in a dispute about the Eastern Church. He had been called upon to decide between two claimants for the Chaldæo-Christian Patriarchate, and wanted to rid himself of such litigation. He therefore declined to interfere in the internal affairs of the Jews and Christians, and decreed that in future each party should be empowered to elect its own religious chief. If ten Jews wished to elect an Exilarch, ten Christians an Archbishop, or ten Fire-worshipers a Chief Priest, they had the power to do so. This decree was unsatisfactory to both parties, inasmuch as it left the quarrel undecided; it is not certain how it ended. So much, however, is known: David ben Judah asserted his authority, and filled the post for about ten years (till 840).