For decades the German philosopher Martin Heidegger has been the subject of passionate debate. His critique of Western thought and technology has penetrated deeply into architecture, psychology and literary theory and inspired some of the most influential intellectual movements of the 20th century. Yet he was also a fervent Nazi.

Now a soon-to-be published book in English has revived the long-running debate about whether the man can be separated from his philosophy. Drawing on new evidence, the author, Emmanuel Faye, argues fascist and racist ideas are so woven into the fabric of Heidegger’s theories that they no longer deserve to be called philosophy. As a result Mr. Faye declares, Heidegger’s works and the many fields built on them need to be re-examined lest they spread sinister ideas as dangerous to modern thought as “the Nazi movement was to the physical existence of the exterminated peoples.”

First published in France in 2005, the book, “Heidegger: The Introduction of Nazism Into Philosophy,” calls on philosophy professors to treat Heidegger’s writings like hate speech. Libraries, too, should stop classifying Heidegger’s collected works (which have been sanitized and abridged by his family) as philosophy and instead include them under the history of Nazism. These measures would function as a warning label, like a skull-and-crossbones on a bottle of poison, to prevent the careless spread of his most odious ideas, which Mr. Faye lists as the exaltation of the state over the individual, the impossibility of morality, anti-humanism and racial purity...