Four intelligence agencies, along with the National Intelligence Council, assess a natural origin for Covid-19. That positioning of the Proximal Origins letter played a significant role in relegating even factual questions about the possibility of a laboratory accident to the conspiracy-theory dustbin. But even 18 months after publishing Proximal Origins, the doubts persisted. None of this proves a lab leak. The Proximal Origins letter asserted that “any type” of lab-based scenario wasn’t plausible.