Concept:
The caste system is a traditional social stratification system found mainly in Indian society.
Step 1:
The caste system includes hereditary status groups with social restrictions and ranking.
Step 2:
Hierarchy, purity and pollution, and marriage restrictions like endogamy are important caste features.
Step 3:
Proletarian Revolution is a Marxist concept related to class struggle between workers and capitalists.
Step 4:
The caste system is based on social hierarchy and ritual status, while proletarian revolution belongs to Marxist political theory.
Step 5:
Therefore, the correct answer is Proletarian Revolution.
\[
\boxed{\text{(4) Proletarian Revolution}}
\]