Political scientists have debated whether citizens can use core principles in lieu of ideological orientations to deduce their policy preferences. The 'General Use' model of public opinion holds that everyone draws equally on core principles to determine their preferences. The 'Expertise Interaction' model holds that the extent to which core principles influence policy preferences is a function of political expertise. Unfortunately, research design and measurement problems in extant work preclude a resolution of this debate. Here I account for these problems, test the predictions of both models, and find empirical support for each. The results demonstrate that while there is a moderate tendency for political expertise to strengthen the relationship between core beliefs and policy preferences, virtually all citizens use core beliefs to deduce preferences.