Philosophical dialogue requires an approach to teaching and learning in science that is focused on problem posing and provides space for meaning making, finding new ways of thinking and understanding and for linking science with broader human experiences. This article explores the role that philosophical dialogue can play in science lessons and the contribution it can make to breaking down barriers between disciplines (why to use philosophical dialogue). It then provides some examples of questions to stimulate philosophical dialogue and suggests some moves that teachers can make to facilitate discussion in whole-class situations (how science teachers can use philosophical dialogue). It is argued that facilitated discussion of philosophical questions can help students to build connections between science, philosophy and their own interests and experiences in science, other disciplines, and their lives.