This article argues that ideology was of key-importance to the Soviet system. The rules which governed Soviet ideological discourse did not only hold for the producers of ideology but also aimed at "filtering' public communication. The respect people showed for an ideologically "filtered' discourse counted as a sign of loyalty. In this way ideology constituted a central pillar of power. The article presents the results of an analysis of political texts dating from the Gorbachev era. It concludes that the Gorbachev reforms eroded the "communication filter' because they changed the rules on which ideological discourse and thus power rested.