One day in April 1969 Theodor Adorno began teaching a new course entitled ‘An Introduction to Dialectical Thinking’. Feel free, the sociologist-cum-philosopher told the packed hall at Frankfurt University, to ask questions as I go. Two of his charges did so immediately. When was Adorno going to apologise for having set the cops on those campus protesters three months earlier? Before Adorno could reply, another student scrawled ‘If Adorno is left in peace, capitalism will never cease’ on the blackboard.