Who among the following is NOT a member of the Frankfurt School?

The correct option is Louis Althusser.

The Frankfurt School, officially known as the Institute for Social Research (Institut für Sozialforschung), is a school of social theory and critical philosophy associated with the University of Frankfurt. Established in 1923, its members developed "Critical Theory," drawing on Western Marxist, Hegelian, Freudian, and Weberian traditions to analyze society, culture, and power structures.

Let's examine the intellectual alignment of the individuals listed in the options:
1. Max Horkheimer was an indispensable director of the Frankfurt School and one of its foundational figures, establishing the core tenets of Critical Theory.
2. Theodor Adorno was a central philosopher and sociologist of the Frankfurt School, co-authoring the seminal work Dialectic of Enlightenment with Horkheimer.
3. Herbert Marcuse was a prominent member of the school's "first generation," renowned for his critique of modern industrial capitalism in works like One-Dimensional Man.
4. Louis Althusser, on the other hand, was a highly influential French Marxist philosopher associated with Structural Marxism. He was affiliated with the French Communist Party and taught at the École Normale Supérieure in Paris, not the Frankfurt School.

Therefore, Louis Althusser is NOT a member of the Frankfurt School.