In this chapter we explore how people build new theories in the context of collaborative scientific thinking. As illustrated by many of the chapters in this volume, our default notion of "scientific thinking" has changed from that of the lone scientist or student toiling away on a magnum opus or in the laboratory, to that of people working as part of collaborative groups who negotiate goals for the task, co-construct knowledge, and benefit from the diverse prior knowledge that each collaborator brings to the table. In some ways, conceptualizing scientific thinking as fundamentally