A series of investigations, especially in Great Britain and the United States, have focused attention on the performance of national intelligence services. At the same time, terrorism and a broad span of trans-national security challenges has highlighted the crucial role of intelligence. This book takes stock of the underlying intellectual sub-structure of intelligence. For intelligence, as for other areas of policy, serious intellectual inquiry is the basis for improving the performance of real-world institutions. The volume explores intelligence from an intellectual perspective, not an organizational one. Instead the book identifies themes that run through these applications, such as the lack of comprehensive theories, the unclear relations between providers and users of intelligence, and the predominance of bureaucratic organizations driven by collection. A key element is the development, or rather non-development, of intelligence toward an established set of methods and standards and, above all, an ongoing scientific discourse.