In a Congressional hearing on Wednesday , Sen. Bernie Sanders (I-Vt.) directly confronted anti-vaccine Health Secretary Robert F. Kennedy Jr. on his rejection of germ theory—the unquestionable scientific idea that specific pathogenic microbes cause specific diseases. After Kennedy defended his fringe view, Senator Bill Cassidy fact-checked and debunked Kennedy’s denialist arguments in real time. The exchanges mark a rare instance in which Kennedy’s dismissal of germ theory has been raised in such a high-profile public setting, in this case, a hearing of the Senate Committee on Health, Education, Labor, and Pensions. Kennedy, who has no background in science, medicine, or public health, is well known as an ardent anti-vaccine activist and peddler of conspiracy theories. But his startling rejection of a cornerstone theory in biomedical science has mostly been underreported. As Ars Technica reported last year , Kennedy wrote about his germ theory denialism explicitly in his 2021 book The Real Anthony Fauci .…