“Their unpopularity grew throughout the eleventh century, as more classes of the community began to borrow money from them; and the beginnings of the Crusading movement added to it. It was expensive for a knight to equip himself for a Crusade; if he had no land and no possessions to pledge, he must borrow money from the Jews. But was it right that in order to go and fight for Christendom he must fall into the clutches of members of the race that crucified Christ? The poorer Crusader was often already in debt to the Jews. Was it right that he should be hampered in his Christian duty by obligations to one of the impious race? The evengelical preaching of the Crusade laid stress on Jerusalem, the scene of the Crucifixion. It inevitably drew attention to the people at whose hands Christ had suffered. The Moslems were the present enemy; they were persecuting Christ’s followers. But the Jews were surely worse; they had persecuted Christ Himself.” 
Jean Richard, Emeritus Professor at the University of Dijon, France, gives a similar rationalizing account, “The motives for these outbursts [of violence] may, of course, be connected to the envy aroused by the wealth of the Jews, and the resentment provoked by their practice of usury. The widespread recourse to credit which began during the course of the eleventh century, and the seemingly brazen prosperity of Jewish moneylenders, no doubt encouraged such explosions, which were not confined to the Christian West; the first great wave of hatred of which the Jews were victims in the eleventh century took place around 1066 in Muslim Spain, at Grenada”. 
Antisemitism is clearly, in part, a result of social and economic tensions, but it is only half the truth. Maurice Samuel in his The Great Hatred   pointed out the inadequacy of the materialist interpretation of antisemitism. Three years later Joshua Trachtenberg, in his classic study, The Devil and the Jews , brought the discussions back to the real source of antisemitism, rumour, superstition, crass credulity, and fanaticism, in other words human irrationality in all its forms: “Hatred of the Jew is not the result of a rational process”¦.No, hatred of the Jew rests upon no rational base. When everything possible has been said about the psychological xenophobia that rejects “˜difference” and resents minority cultures, about economic and social frictions that exacerbate social relations, about the astute and persuasive propaganda techniques of anarchical demagogues, about the need for a “scapegoat” for release of social tension, about the imperfections of the Jews themselves, and their abnormal economic status — and all these are potent immediate stimuli of active Jew hatred–the ultimate source, buried deep in the mass subconscious, is still untouched. Underneath the present stimuli, and contributing to them their explosive potentiality, lies the powder keg of emotional predisposition, of a conception of the Jew which has nothing to do with facts or logic”. 
Ironically, while Sir Steven argues that Christianity was responsible for Islamic intolerance, Trachtenberg suggests that one of the contributing factors to the rise of Christian antisemitism in the later Middle Ages was “the rising menace of Islam”.  Christian antisemitism reached its apogee in the post-Crusade period, but it was the result of centuries of demonisation of the Jew as devil, sorcerer, and ritual murderer.
 Steven Runciman. A History of the Crusades, Vol. I, The First Crusade and the Foundation of the Kingdom of Jerusalem, Cambridge: Cambridge University Press, 1951, pp.134-35.
 Jean Richard. The Crusades c.1071-c.1291, Cambridge: Cambridge University Press, 1999, p.39.
 Maurice Samuel [died 1972], The Great Hatred. New York: Alfred A.Knopf, 1940.
 Joshua Trachtenberg, [died 1959], The Devil and the Jews. The Medieval Conception of the Jew and Its Relation to Modern Antisemitism. [Original Edn. 1943, Yale University Press], New York: Harper Torchbook, 1966.
 Joshua Trachtenberg, op.cit., pp. 2-3.
 Ibid., p. 11.
To be continued.