Although "post-truth" became Oxford Dictionary's word of the year only in 2016, the concept is endemic to the history of Western thought, albeit typically existing in an underground and somewhat disreputable state. From the ancient Sophists to the "constructivist" turn across many disciplines in the 20th century, post-truth has always been with us, however much we wish to deny its presence. This talk, drawn from Fuller's new book on "post-truth," explains and -- to a large extent -- justifies the value of the post-truth condition, notwithstanding the political aberrations nowadays associated with it, not least Brexit and Trump.