Trained as a mathematician, Alain Badiou is one of the most original French philosophers today. Influenced by Plato, Georg Wilhelm Friedrich Hegel, Jacques Lacan and Gilles Deleuze, he is an outspoken critic of both the analytic as well as the postmodern schools of thoughts. His philosophy seeks to expose and make sense of the potential of radical innovation (revolution, invention, transfiguration) in every situation.I read Being and Event a couple of years ago, as it can be found as a pdf, and I had recalled mention of Badiou by Alan Sokal and Jean Bicmont in their 1998 book Intellectual Impostures.
Anyway, I'd forgotten him until recently, but had an occasion to watch a Youtube video, "Infinity and Set Theory: How to Begin with the Void" of Badiou giving a 2011 talk concerning set theory and "the void" (a transcript is here).
Here is a snapshot I took of the talk (at 53:05). What's wrong with it? Don't cheat! (Hint below)
$\varnothing$It doesn't even seem to be a typo or a spelling mistake, as he keeps repeating it.
(I make plenty of spelling mistakes - a friend on facebook keeps correcting my rubbish English ...)