Last week, Sen. Rand Paul and National Institute of Allergy and Infection Diseases Director Anthony Fauci went at it again. This time, the issue was whether or not the nation’s top doctor had allowed funding for gain-of-function research at the Wuhan Institute of Virology in China.

Paul believes that his sources, including Fauci’s private emails published by Buzzfeed in June, support the idea that Fauci approved the funding. The doctor denies it. The Republican senator reminded Fauci that lying to Congress was a crime. Fauci was unmoved. “If anyone is lying here, senator,” he responded, “it is you.”