Althusser argues that no class can hold power for any length of time simply by the use of force. Ideological control provides a far more effective means of maintaining class rule.
If members of the subject class accept their position as normal, natural and inevitable, and fail to realize the true nature of their situation, then they will be unlikely to challenge ruling class dominance.
Physical force is an inefficient means of control compared to winning over hearts and minds. The maintenance of class rule largely depends on the reproduction of ruling class ideology.