The Snowden Affair, Wikileaks, the 'lone wolf' terrorist, Clinton's private email account - the secret is arguably the central element of our contemporary political experience. Now, Charles Barbour looks at the basic ontological question 'what is a secret?' Organised as a reflection on Jacques Derrida's later writings on secrecy, four chapters each look at a separate problematic: society and the oath, literature and testimony, philosophy and deception, and time and death. Barbour shows that secrecy is not a negation of our relations with others, but a necessary condition of those relations. We can only reveal ourselves to one another (and, indeed, to anything other) insofar as we conceal as well.