This chapter spells out the notion of the espistemology of the secret. It unpacks the two main components of the epistemology of the secret of international law: the necessary presence of hidden, unknown, invisible content in the texts, practices, actors, effects, representations, past, etc. of international law (what is called in this book the necessity of secret content) and the necessity for international lawyers to reveal such hidden, unknown, invisible content (what is called in this book the necessity of revelation). The chapter distinguishes the epistemology of the secret of international law from the hermeneutics of suspicion, the idea of an ideology of secretism and the idea of an economy of secrets.