He criticizes Sigmund Freud, arguing that psychoanalysis is a branch of the humanities rather than a science, and provides a critique of the philosopher Friedrich Nietzsche.

Habermas's first major systematic work, Knowledge and Human Interests has been compared to the philosopher Paul Ricœur's Freud and Philosophy (1965).

However, critics have found Habermas's attempt to discuss the relationship between knowledge and human interests unsatisfactory, and his work obscure in style.

In his view, rationalism and empiricism were both concerned with "the metaphysical demarcation of the realm of objects and the logical and psychological justification of the validity of a natural science characterized by formalized language and experiment.

[6] According to Habermas, he first expounded the views he developed in the book in his Frankfurt inaugural address of June 1965, while his discussion of positivism, pragmatism and historicism had its origins in lectures he delivered in Heidelberg in 1963 and 1964.

[12] Jandt found the book promising, though he considered it difficult to assess because of Habermas's competence in fields ranging from the logic of science to the sociology of knowledge.

He believed that it formed part of a body of work which "comprises a dialectic sufficiently rigorous to indict and perhaps dislodge behavioral and scientistic theories of communication.

He wrote that, "Its style is unnecessarily obscure and high-flown, its lack of fine-grained philosophical analysis disappointing, and its concentration on the exegesis of other thinkers essentially diversionary."

[11] Martin argued that the work reflected the "impasse of the sociology of knowledge" and failed to explain how transforming social relations would make objectivity possible.

[12] Knowledge and Human Interests was discussed by Paul Ricœur in the Journal of the American Psychoanalytic Association,[13] Rainer Nagele, Roland Reinhart, and Roger Blood in New German Critique,[14] Kenneth Colburn Jr. in Sociological Inquiry,[15] Steven Vogel in Praxis International,[16] Richard Tinning in Quest,[17] Jennifer Scuro in The Oral History Review,[18] and Myriam N. Torres and Silvia E. Moraes in the International Journal of Action Research.

[22] Torres and Moraes described Knowledge and Human Interests as a "seminal work", and credited Habermas with providing "the theoretical framework for understanding curriculum and educational research.

[26] The philosopher Douglas Kellner credited Habermas with demonstrating the importance of psychoanalysis for "increasing understanding of human nature and contributing to the process of self-formation".

"[29] The philosopher Jonathan Lear blamed Knowledge and Human Interests, along with Ricœur's Freud and Philosophy, for convincing some psychoanalysts that reasons cannot be causes.