C. Wright Mills, in his seminal work 'The Power Elite' (1956), argued that power in modern industrial societies, particularly the United States, is concentrated in the hands of a small, interconnected group of individuals whom he termed the 'power elite.' His assertion that "Elites rule in institutional terms rather than psychological terms" is central to his theory and distinguishes it from other explanations of power.

Understanding "Institutional Terms": Mills contended that the power of the elite does not stem from their individual psychological traits, charisma, or inherent superiority. Instead, their power is derived from the positions they occupy within the dominant institutions of society. He identified three key institutional spheres where power is concentrated:

1. The Economic Elite: Leaders of major corporations, who control vast economic resources and influence national and international markets.
2. The Political Elite: Top government officials, including the President, cabinet members, and key bureaucrats, who wield legislative and executive power.
3. The Military Elite: High-ranking officers in the armed forces, who command immense coercive power and influence foreign policy.

Mills argued that these institutional leaders are interconnected through shared backgrounds, social networks, and a common worldview. They often move between these spheres (e.g., a corporate CEO becoming a cabinet secretary, a general joining a corporate board), creating an 'interlocking directorate' that solidifies their collective power. Their decisions are shaped by the structural imperatives, resources, and organizational logic of the institutions they command, rather than purely personal whims.

Rejecting "Psychological Terms": By emphasizing institutional power, Mills explicitly rejected explanations that attribute elite rule to individual psychological attributes such as ambition, intelligence, leadership skills, or a 'will to power.' He also critiqued the idea that power is diffused among many competing interest groups (pluralism) or that it resides in the 'will of the people' in a truly democratic sense. For Mills, the individual characteristics of the elite members were secondary to the structural power inherent in their institutional roles. It is the control over the means of production, the state apparatus, and the instruments of violence that grants them power, not their personal charm or intellect.

Implications: Mills's perspective highlights that power is systemic and structural. It suggests that merely changing individual leaders without altering the institutional arrangements that concentrate power will not fundamentally change who rules or how decisions are made. His theory underscores how the very structure of modern society, with its large-scale organizations and centralized decision-making, facilitates the emergence and perpetuation of a powerful elite, regardless of the specific personalities involved. This institutional focus provides a critical lens for understanding the enduring nature of power disparities in society.