On 12 November 1671 the Prince-elector Johann Philipp of Schönborn decided to reduce the Jewish population of Mainz to ten households, who henceforth should live together in a segregated and enclosed lane, i. e. a ghetto. Historians have struggled to understand the reason for Schönborn’s »anti-Jewish policy«, since during the Middle Ages, Jews were allowed to live next to their Christian neighbours and to own real estate anywhere across the city. According to Siegmund Salfeld, this measure was an act of pure discrimination and Johann Philipp – well known for his tolerance and therefore called the »German Solomon« – was simply an »enemy of the Jews«. However, such historiographical characterizations do not account for the complicated motives for the ghettoization . Indeed, in the territories of the Holy Roman Empire Jews generally were not the target, but rather functioned as an object or instrument of sovereign policy. Even the expulsion of the Jewish population from Vienna ordered by Emperor Leopold I in 1670 cannot be considered a result of his personal hostility against Jews. Rather, this fatal treatment of the Jewish inhabitants and the subsequent development of the Leopoldstadt , are best explained as a consequence of political pressure resulting from the complaints of citizens, as well as from the Emperor’s urban planning which was informed by mercantilist ideas. As this reconstruction demonstrates, research and interpretation of the imperial princes’ »Jewish policy« has to consider and integrate aspects of public, social and economic policy. The ambiguous historiographic term »Jewish policy« can therefore not be used in any historical context, because two preconditions are required for this: 1) a (proto-)modern territorial state based on effective administration and aiming at the common good , 2) a partially estate-based society defining the Jews as a specific religious, legal, or sociocultural group.