Book excerpt: In today's transnational world, a sustainable national security policy cannot be achieved through national capabilities alone. Sustainable national security instead rests on three pillars: 1) a multi-sum security principle based on justice at all levels, multilateralism and multidimensionality (including human, environmental, national, transnational and transcultural/transcivilizational security); 2) symbiotic realism in international relations, whereby mutual cooperation among states results in non- conflictual absolute gains; and 3) transcivilizational synergy which results from mutual respect, multiculturalism, cosmopolitanism and cross-fertilization, and will lead to global justice, security and prosperity. This well-written and cogently-argued book captures the complex challenges facing our leaders today and in the future, and it delivers a strong set of recommendations for a much-needed reorganisation of national security decision making to make it more responsive and effective. It will be essential reading for anyone interested in an innovative approach to the complex yet central subject of sustainable national security.