The statement that "vertical mobility brings structural change even in a closed social system" presents a nuanced and somewhat contradictory idea, requiring careful comment. Vertical mobility refers to movement up or down the social hierarchy, while a closed social system, by definition, is characterized by rigid boundaries and limited opportunities for such movement, often based on ascription (e.g., birth, caste).

In a truly closed social system, individual vertical mobility is severely restricted, and the system's structure is designed to maintain the existing hierarchy. For instance, in a rigid caste system, an individual's status is determined at birth, and upward mobility is virtually impossible, thereby preserving the structural integrity of the system. If significant vertical mobility were to occur frequently, the system would cease to be 'closed' in its strict sense.

However, one could argue for a more subtle interpretation. Even in seemingly closed systems, minor, localized, or exceptional instances of vertical mobility might occur due to various factors like individual talent, patronage, or slight shifts in occupational structures over very long periods. For example, in India, the concept of 'Sanskritization' describes how lower castes might adopt the customs of higher castes to claim a higher status, which represents a form of collective, albeit slow and often contested, upward mobility. While such instances might bring about micro-level changes or individual status shifts, they do not necessarily lead to fundamental structural change in the system itself, meaning the basic principles of hierarchy and ascription remain intact.

For structural change to occur in a closed system, it typically requires more than just individual vertical mobility. It demands a transformation of the underlying rules, norms, and power dynamics that define the system's closure. This usually happens due to external pressures (e.g., colonial policies, globalization), internal contradictions, or large-scale social movements that challenge the very foundations of the system. Therefore, while limited vertical mobility might exist even in rigid systems, it is generally insufficient to bring structural change; rather, widespread structural change is what opens up a previously closed system to greater mobility.