As they were not Christians , they were not included as a division of the feudal system of clergy , knights and serfs .
Between 800 and 1100 , an estimated 1.5 million Jews lived in Christian Europe .
As Jews were not Christian , Jews were not included as a division of the feudal system of clergy , knights and serfs .
Between 800 and 1100 , an estimated 1.5 million Jews lived in Christian Europe .