In the introduction to this chapter, diSessa, Levin, and Brown discusses six ways in which relations between the research programs of knowledge analysis (KA) and interaction analysis (IA) could be understood. The relation that they label 'micro-complementarity' seems promising to them, and author agree. Another example is an analysis by Greeno, Melissa Sommerfeld, and Muffie Wiebe of an interaction involving four middle-school students working on mathematical problems of population biology in a curriculum that included constructing models of population growth and decline. The data considered here were results obtained in a study of learning that focused on students' modeling activities in a project-based middle-school mathematics classroom. The chapter focuses on two episodes involving the student group known as MLKN (Manuel, Lisa, Kera, and Nick). While Sandra Mitchell argues pluralism, in the sense that some alternative theories can be understood as being complementary, she also argues integrative pluralism, in the sense that integration of theories is an important scientific goal.