The social sciences study phenomena, structures, institutions, and action in the realm of human affairs through an evolving set of frameworks and concepts. Some of these building blocks of social scientific enquiry were introduced to students in the first core course of the major. In this course, we build upon that learning and focus on certain key concepts and ideas in the social sciences. The design of this second semester course adopts a toolbox approach. In that, from a vast array of available conceptual instruments developed by different constitutive social science disciplines and interdisciplinary domains, only a small selection is presented to students. The rationale for this selection is based upon identifying the basic conceptual vocabulary and theoretical foundation students in the Social Science major require to productively engage with subsequent courses in the curriculum. Along with Seeing Like a Social Scientist and Statistics for Social Science, Key Concepts in the Social Sciences complete the set of foundational courses for Social Science majors in their first year of study.