Alain Badiou is arguably the most original and influential philosopher working in France today. Working against the tide of postmodern orthodoxy, Badiou revitalizes philosophy's perennial attempt to provide a systematic theory of truth. presents, in Badiou's own words, 'the theoretical core of [his] Philosophy'. Beginning with the controversial assertion that ontology is mathematics, the chapters step the reader through his key concepts of being, subject and truth via startling re-readings of canonical figures including Spinoza, Kant and Hegel and engagements with poetry, psychoanalysis and radical politics. is an indispensable introduction to one of the great thinkers of our time.