Renowned French physicist and science communication star Étienne Klein has had his PhD revoked by Paris Cité University after an academic investigation that lasted about 20 months because of extensive plagiarism in his doctoral thesis.
Klein is a physicist at the French Atomic Energy and Alternative Energy Commission (CEA) and a highly influential science communicator. He has published more than 30 popular science and philosophy books, and hosts a weekly science talk program on French Culture Radio. He has enjoyed a high reputation among the media and the public for many years. As early as 2016, he had been accused of plagiarizing other people's words in popular science works many times, but it was not until the summer of 2024 that the media extended doubts to his academic papers themselves.
In August 2024, the French media "Arrêt sur images" conducted a line-by-line comparison of Klein's doctoral thesis in the philosophy of science completed in 1999 and found that about 20% of the pages in the paper contained plagiarized fragments. The text sources involved included the writer Albert Camus, the physicist Louis de Broglie, and even some members of his thesis defense committee. The media subsequently published a long article disclosing its investigation results and showing the public specific comparison clips, which shocked public opinion and prompted the University of Paris to launch a formal investigation process.
After launching an internal investigation, the University of Paris organized experts to conduct a comprehensive review of the doctoral thesis. Based on internal information later obtained by multiple media outlets, the unpublished investigation report stated that plagiarized content was found in nearly two-thirds of the paper pages, far exceeding the proportion previously disclosed during self-checks by the media. In June 2026, Image Observer quoted anonymous sources as saying that the school had determined that Klein had committed plagiarism and officially revoked his PhD. The French newspaper Le Monde also confirmed the general direction of the review conclusion from another independent source.
In the face of media inquiries, the University of Paris did not directly announce the conclusion of the investigation, but it also did not deny the report of revoking the degree. School principal Edouard Kaminski said in an email reply to Science magazine that the school could not comment publicly or disclose details due to legal restrictions on specific individuals and relevant information, but he also pointed out that the school "has not issued any statement denying media reports." This statement was regarded by the outside world as a de facto acquiescence to the decision to cancel.
Regarding this incident, Klein did not respond to multiple requests for comment from Science magazine. However, he published a four-page open letter through the social platform In the letter, he elaborated on his views on the accusations, but never directly used the word "plagiat."
This is not the first time that Klein has been formally punished for academic and writing ethics issues. About a decade ago, the French weekly L’Express revealed that he had plagiarized passages in numerous popular science books and columns, including a biography of Albert Einstein. Klein was removed as director of the Institute for Advanced Studies for Science and Technology in 2017 following an independent investigation commissioned by France's Ministry of Higher Education and Research, although he retained his research position at the Atomic and Alternative Energies Commission.
Despite the previous turmoil, Klein's public image and communications career remained virtually unaffected in the years that followed. Since 2016, he has published more than ten popular science and essay works, and continues to serve as a science program host on French Culture Radio. In 2020, the French Academy of Ethics and Political Science also awarded him a Physics Essay Prize, further solidifying his status as an authority in the world of science popularization in the French-speaking world.
Because of this, after the new round of plagiarism investigation results came out, some observers pointed the finger at publishing houses and media organizations that have long cooperated with Klein. Science philosopher Olivier Saltner of the University of Namur in Belgium pointed out that although accusations of plagiarism have long surfaced, many well-known French publishing houses and media have continued to cooperate with Klein in publishing and producing programs to maintain his image as a "well-respected" scientific authority at the public level. This undoubtedly sends a signal of nepotism or excessive tolerance in the eyes of the outside world.
Now, with the doctorate revoked, Klein's partner institutions are beginning to reassess their position. In an email reply to Science magazine, Radio France Culture said it had "taken note" of the university's decision and was "reviewing the current situation." The Atomic and Alternative Energy Commission said it had been informed of the university's sanctions and was "considering next steps." The outside world is generally concerned about whether these institutions will further take more stringent personnel or cooperation measures.
In the open letter, Klein tried to respond to external doubts through a discussion of "unconscious absorption." He claimed that he had read a lot of books during his career, which he may have "digested" and used "not always consciously" in his writing. He also questioned why his doctoral thesis became the subject of magnified scrutiny while other people's dissertations were not subject to similar scrutiny. He called critics "quotation mark fanatics" and accused them of only focusing on the details of their own words instead of dealing with those who actually spread scientific false information. He also argued that his work was factually error-free and had played an active role in combating scientific misinformation.
The response met with little sympathy among academics. Saltner believes that Klein's appeal to the so-called "unconscious borrowing" and "combating disinformation" is a logically untenable argument that will only send an extremely bad signal to students and researchers. In his view, the University of Paris still chose to take severe action by revoking his degree when facing a scholar with a high profile and huge public influence. This was a "courageous decision" that would help rebuild public trust in academic institutions in handling misconduct. As he said, this incident shows that even if the system works well, even academic stars cannot completely stay outside academic norms.