Defining System 2 deliberation for dual-process models

Deliberation, commonly referred to as "System 2" thinking, is a core component of popular dual-process models of reasoning. However, its precise conceptualization has received limited attention. In this perspective, I present a basic framework and organizing principles to think of deliberation and avoid problematic misconceptions. I argue that deliberation should be understood as multifunctional, serving multiple, complementary purposes. I highlight four such functions (response control, response generation, response justification, and regulation), identify challenges in our current understanding, propose guiding principles, and discuss critical outstanding questions. The resulting framework should help advance the theoretical and empirical study of deliberation in the coming years.