Oskar Kraus (1872-1942) was probably the most original representative of the orthodox Brentano school.
Not only did he render outstanding service as co-editor of Franz Brentano's posthumous writings, but he also brought Brentano's value-theoretic approach to bear on ethics, philosophy of law, and economics. In his major work published in 1937, Die Werttheorien.History and Critique", published in 1937, Oskar Kraus reconstructs Brentano's value-theoretical approach in detail and outlines a critical history of value theory from antiquity to the 20th century.At its center is a confrontation with the relativist theories of his contemporaries, for Kraus saw Brentano's approach to the justification of value as a means of countering this ethical relativism.

Oskar Kraus belonged to the second generation of the Brentano school. In addition to law, he also studied philosophy with Anton Marty in Prague. Anton Marty was one of the most important philosophers of the time, alongside other prominent philosophers such as Edmund Husserl, Thomas G. Masaryk and Christian von Ehrenfels, he was one of the first generation of the Brentano School and is considered to be Franz Brentano's most faithful disciple.

This most important work by Oskar Kraus is important for Brentano research on the one hand. However, it is also aimed at graduate students and academics interested in the foundations of ethics or in the history of moral philosophy in general, and the history of the nineteenth and twentieth centuries in particular. The book is introduced by Thomas Binder and Hynek Janoušek, who have made numerous contributions to contemporary Brentano scholarship.