… is from page 230 of Thomas Sowell’s excellent 1987 volume, A Conflict of Visions:
Yet, in the long run, these ideological conflicts seem to shape the general course of political trends as much as “practical” political considerations dominate day-to-day events. To a considerable extent, the ideological presuppositions of the times set the limits and the agenda which determine what is feasible, realistic, or imperative to practical politicians.
In short, ideas matter significantly.