ABSTRACT
This chapter explains how realists understand security, specifically, the meaning of the term itself, the factors that influence a state's ability to be secure, and the strategies that states can pursue to achieve security. Realism is the longest standing and arguably the best developed of the various approaches for understanding international security. The chapter reviews realism's core assumptions and explains how they are related to the expansion of security studies. It looks at the security dilemma, specifically the role of information about other states' motives in driving the security dilemma. The security dilemma depends on both material and information variables. The chapter briefly sketches the divergent strands of the realist family and assesses why they disagree. It considers realism's continuing analytic value for understanding and responding to ongoing changes in international politics. Reviewing realism's basic assumptions sets the stage for understanding its lack of conceptual expansion.
